Antibodies

ABSTRACT

The present invention relates to antibodies binding to 5T4, including bispecific antibodies binding to 5T4 and CD3. The invention further provides pharmaceutical compositions comprising the antibodies and use of the antibodies for therapeutic and diagnostic procedures, in particular in cancer therapy.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.16/813,167, filed Mar. 9, 2020, which is a continuation of InternationalApplication No. PCT/EP2019/056197, filed Mar. 12, 2019, which claimspriority to European Patent Application Nos. 18161293.8 and 18175347.6,filed on Mar. 12, 2018, and May 31, 2018, respectively. The contents ofthe aforementioned applications are hereby incorporated by reference.

SEQUENCE LISTING

The instant application contains a Sequence Listing which has beensubmitted electronically in ASCII format and is hereby incorporated byreference in its entirety. Said ASCII copy, created on Oct. 22, 2020, isnamed GMI_190PCCNDV_Sequence_Listing.txt and is 90, 399 bytes in size.

FIELD OF INVENTION

The present invention relates to antibodies binding to 5T4, includingbispecific antibodies binding to 5T4 and CD3. The invention furtherprovides pharmaceutical compositions comprising the antibodies and useof the antibodies for therapeutic and diagnostic procedures, inparticular in cancer therapy.

BACKGROUND

5T4 (also known as trophoblast glycoprotein [TPBG] or Wnt-activatedinhibitory factor 1 [WAIF1]) is a 72 kDa, single-pass transmembraneprotein that contains 8 leucine-rich repeats (LRR) and 7 potentialN-glycosylation sites (Zhao et al., 2014 Structure 22, 612-620).

5T4 expression is limited in normal adult tissues, except for placenta(Southall et al., 1990 Br J Cancer 61, 89-95). 5T4 is expressed in manyhuman cancers, including renal, cervical, ovarian, lung, prostate andcolon cancer (Stern and Harrop, 2017 Cancer Immunol Immunother 66,415-426; Southall et al., 1990 Br J Cancer 61, 89-95). 5T4 expression intumor cells drives tumor development by 1) facilitatingepithelial-to-mesenchymal transition (Damelin et al., 2011 Cancer Res71, 4236-4246; Carsberg et al., 1996 Int J Cancer 68, 84-92), and 2)inhibition of the canonical Wnt/beta-catenin signaling pathway andactivation of the non-canonical Wnt pathway (Kagermeier-Schenk et al.,2011 Dev Cell 21, 1129-1143). 5T4-targeting antibodies and 5T4-targetingtherapies have clinical activity in several cancers known to express 5T4(including colorectal, lung and renal cancer). For example, naptumomabestafenatox is a recombinant fusion protein that consist of the 5T4-Fabmoiety genetically fused to the engineered superantigen variantSEA/E-120. It is currently in clinical trials as an immunotherapy fornon-small cell lung cancer (NSCLC), renal cell (RCC) and pancreaticcancer (see e.g. Eisen, et al., 2014 Curr Oncol Rep 16, 370).Furthermore, TroVax® is a modified vaccinia Ankara that expresses 5T4constructs (MVA-5T4), which shows clinical benefit in colorectal,prostate and renal cancer (see e.g. Stern and Harrop, 2017 CancerImmunol Immunother 66, 415-426; Scurr et al., 2017 JAMA Oncol 12, 10).Further anti-5T4 antibodies have been described in WO2007106744,WO03038098, WO2011048369, WO2013041687, WO2017072207.

While significant progress has been made on eradication of cancer, thereis still a need for further improvement of antibody-based cancertherapy.

SUMMARY OF INVENTION

It is an object of the present invention to provide an antibodycomprising at least one antigen-binding region capable of binding to 5T4(Trophoblast glycoprotein), wherein the antibody is able to blockbinding to 5T4 of an antibody comprising a variable heavy chain (VH)region comprising the sequence set forth in SEQ ID NO: 5, and a variablelight chain (VL) region comprising the sequence set forth in SEQ ID NO:9 [059].

The antibody may in particular be a bispecific antibody and may furthercomprise an antigen binding region of an antibody that binds to CD3,such as human CD3ε (epsilon), such as human CD3E (epsilon) as specifiedin SEQ ID NO: 4.

In another aspect, the present invention relates to a nucleic acidconstruct comprising

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein, and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein.

In another aspect, the present invention relates to an expression vectorcomprising

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined hererin, and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein.

In another aspect, the present invention relates to a cell comprising anucleic acid construct or an expression vector as defined herein.

In another aspect, the present invention relates to a compositioncomprising an antibody according to the invention.

In another aspect, the present invention relates to a pharmaceuticalcomposition comprising an antibody as defined herein and apharmaceutically acceptable carrier.

In another aspect, the present invention relates to an antibody asdefined herein for use as a medicament, such as for use in the treatmentof a disease.

In another aspect, the present invention relates to a method of treatinga disease or disorder, the method comprising administering an antibody,a composition or pharmaceutical composition as defined herein, to asubject in need thereof.

In another aspect, the present invention relates to methods forproducing an antibody as defined herein.

In another aspect, the present invention relates to a kit-of-parts,comprising an antibody as defined herein; and instructions for use ofsaid kit.

In another aspect, the present invention relates to an anti-idiotypicantibody, which binds to the antigen-binding region capable of bindingto 5T4 of the antibody as defined herein.

BRIEF DESCRIPTION OF FIGURES

FIGS. 1A-1C: Antibody displacement of IgG1-5T4-059-FEAR,IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR in combination withIgG1-5T4-A3-F405L. Antibody displacement was determined by biolayerinterferometry on an Octet HTX instrument (ForteBio). IgG1-5T4-A3-F405Lwas immobilized on the biosensor and loaded with human 5T4ECDHis (matureprotein of SEQ ID NO. 99). Subsequently, the loaded biosensors wereexposed to IgG1-5T4-A3-F405L, IgG1-5T4-H8-FEAR, IgG1-5T4-059-FEAR,IgG1-5T4-207-FEAR or IgG1-5T4-226-FEAR. The figure shows the associationresponses (500 s) upon exposure to the second antibodies. FIGS. 1A-1C.IgG1-5T4-A3-F405L showed no binding to the immobilizedIgG1-5T4-A3-F405L-5T4ECDHis complex, indicating cross-block (self-block)with IgG1-5T4-A3-F405L. IgG1-5T4-H8-FEAR antibodies showed an increasein mass (indicating binding to the immobilizedIgG1-5T4-A3-F405L-5T4ECDHis complex) and hence no cross-block withIgG1-5T4-A3-F405L. FIG. 1A. IgG1-5T4-059-FEAR, FIG. 1B.IgG1-5T4-207-FEAR and FIG. 1C. IgG1-5T4-226-FEAR all showed an initialincrease in mass (indicating binding of the antibodies to theimmobilized IgG1-5T4-A3-F405L-5T4ECDHis complex) followed by a rapiddecrease in mass. This behavior of the antibodies is indicative ofantibody displacement (Abdiche Y N, et al. (2017) Antibodies TargetingClosely Adjacent or Minimally Overlapping Epitopes Can Displace OneAnother. PLoS ONE 12(1): e0169535. doi:10.1371/journal.pone.0169535).

FIG. 2: Simultaneous binding of 5T4 antibodies to membrane-bound 5T4measured with flow cytometry. 5T4 antibodies IgG1-5T4-H8-FEAR,IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR were conjugated to fluoresceinisothiocyanate (FITC) and added at a concentration of 2 μg/mL to5T4-expressing SK-OV-3 cells in presence of 10 μg/mL unconjugatedIgG1-5T4-H8-FEAR, IgG1-5T4-A1-F405L, IgG1-5T4-A3-F405L, IgG1-b12,IgG1-5T4-207-FEAR or IgG1-5T4-226-FEAR. Percentage binding ofFITC-labeled antibodies was calculated and depicted as mean percentagebinding±standard deviation (SD).

FIGS. 3A and 38: Binding of 5T4 antibodies to HEK-293 cells transfectedwith full length human and chicken 5T4. HEK-293 cells transientlytransfected with full length human 5T4 (SEQ ID NO: 1) (FIG. 3A) orchicken 5T4 (SEQ ID NO: 3) (FIG. 3B) were incubated with variousconcentrations of IgG1-5T4-A3-F405L, IgG1-5T4-059-FEAR,IgG1-5T4-207-FEAR or IgG1-5T4-226-FEAR antibodies. After incubation withR-Phycoerythrin (PE)-conjugated goat-anti-human IgG F(ab′)2, the meanfluorescence intensity (MFI) was determined by flow cytometry. Asnegative control, IgG1-b12-K409R (10 μg/mL) was included.

FIGS. 4A and 48: Internalization capacity of monovalent 5T4 antibodies.Bispecific, toxin-conjugated antibodies that recognize 5T4 with oneFab-arm while recognizing an irrelevant antigen (HIV-1 gp120, which isnot expressed on tumor cells) with the second Fab-arm, were generated bycontrolled Fab-arm exchange of unconjugated 5T4 antibodies with (HIV-1gp120-specific) IgG1-b12 antibodies that had been conjugated with oneDuostatin-3 molecule per antibody. MDA-MB-468 (FIG. 4A) and HCC1954(FIG. 4B) cells were incubated with increasing concentrations ofantibodies, as indicated. Cell viability was measured after 5 days. Dataare presented as mean percentage viable cells of three replicateexperiments. As negative control, monospecific, bivalent IgG1-b12conjugated with Duostatin-3 (IgG1-b12-vcDuo3) was included.

FIGS. 5A-5D: Binding of CD3×5T4 bispecific antibodies to full lengthhuman and cynomolgus monkey 5T4 transfected into HEK-293 cells. Bindingof monovalent and bivalent 5T4 antibodies was analysed using HEK-293cells transiently transfected with full length human (left panels) orcynomolgus monkey 5T4 (right panels). Cells were incubated withincreasing concentrations of antibodies, as indicated. After secondarylabelling with FITC conjugated goat-anti-human IgG F(ab′)2, binding wasanalysed by flow cytometry. As negative control antibody, IgG1-b12-K409R(3 μg/mL) was included. Data are presented as mean fluorescenceintensity (MFI) values of two technical replicates±SD. FIG. 5A. Bindingof bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR and IgG1-5T4-207-FEAR. FIG. 5B.Binding of bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEAR.FIG. 5C. Binding of bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andIgG1-5T4-059-FEAR. FIG. 5D. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-H8-FEAR and IgG1-5T4-H8-FEAR.

FIGS. 5E-5M: Binding of bispecific CD3×5T4 antibodies to cynomolgusmonkey and human 5T4 transfected into HEK-293 cells. Mono- and bivalentbinding of 5T4 antibodies was analysed using HEK-293 cells transientlytransfected with human 5T4 (left panels) or with cynomolgus monkey 5T4(right panels). Cells were incubated with increasing concentrations ofantibodies, as indicated. After secondary labelling with phycoerythrin(PE)-conjugated goat-anti-human IgG F(ab′)2, binding was analysed byflow cytometry. FIG. 5E. Binding of bsIgG1-huCD3-H101G-FEALx5T4-207-FEARand IgG1-5T4-207-FEAR; FIG. 5F. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEAR; FIG. 5G.Binding of bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR;FIG. 5H. Binding of bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR andIgG1-5T4-106-FEAR; FIG. 5I. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-076-FEAR and IgG1-5T4-076-FEAR; FIG. 5J.Binding of bsIgG1-huCD3-H101G-FEALx5T4-085-FEAR and IgG1-5T4-085-FEAR;FIG. 5K. Binding of bsIgG1-huCD3-H101G-FEALx5T4-127-FEAR andIgG1-5T4-127-FEAR; FIG. 5L. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR and IgG1-5T4-A1-FEAR; FIG. 5M.Binding of bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR and IgG1-5T4-A3-FEAR.

FIGS. 6A-6C: Binding of CD3×5T4 bispecific and 5T4 monospecificantibodies to 5T4-positive human tumor cells. Mono- and bivalent bindingof 5T4 antibodies to HeLa cells (left panels) or MDA-MB-231 cells (rightpanels) was determined by flow cytometry. Cells were incubated withincreasing concentrations of antibodies. After secondary labelling withFITC-conjugated goat-anti-human IgG F(ab′)2, the MFI was determined byflow cytometry. FIG. 6A. Binding of bsIgG1-huCD3-H101G-FEALx5T4-207-FEARand IgG1-5T4-207-FEAR antibodies to HeLa cells (left panel) orMDA-MB-231 cells (right panel). FIG. 6B. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR antibodies toHeLa cells (left panel) or MDA-MB-231 cells (right panel). FIG. 6C.Binding of bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEARantibodies to HeLa cells (left panel) or MDA-MB-231 cells (right panel).IgG1-b12-K409R (3 μg/mL) was included as negative control (opencircles).

FIGS. 6D-6K: Binding of CD3×5T4 bispecific and 5T4 monospecificantibodies to HeLa cells. Mono- and bivalent binding of 5T4 antibodiesto HeLa cells was determined by flow cytometry. Cells were incubatedwith increasing concentrations of antibodies. After secondary labellingwith Phycoerythrin (PE)-conjugated goat-anti-human IgG F(ab′)2, the meanfluorescence intensity (MFI) was determined by flow cytometry. FIG. 6D.Binding of bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR and IgG1-5T4-207-FEAR;FIG. 6E. Binding of bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR andIgG1-5T4-226-FEAR; FIG. 6F. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR; FIG. 6G.Binding of bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR and IgG1-5T4-106-FEAR;FIG. 6H. Binding of bsIgG1-huCD3-H101G-FEALx5T4-085-FEAR andIgG1-5T4-085-FEAR; FIG. 6I. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-127-FEAR and IgG1-5T4-127-FEAR; FIG. 6J.Binding of bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR and IgG1-5T4-A1-FEAR;FIG. 6K. Binding of bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR andIgG1-5T4-A3-FEAR

FIGS. 6L-6S: Binding of CD3×5T4 bispecific and 5T4 monospecificantibodies to MDA-MB-231 cells. Mono- and bivalent binding of 5T4antibodies to MDA-MB-231 cells was determined by flow cytometry. Cellswere incubated with increasing concentrations of antibodies. Aftersecondary labelling with PE-conjugated goat-anti-human IgG F(ab′)2, themean fluorescence intensity (MFI) was determined by flow cytometry. FIG.6L. Binding of bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andIgG1-5T4-207-FEAR; FIG. 6M. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEAR; FIG. 6N.Binding of bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR;

FIG. 6O. Binding of bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR andIgG1-5T4-106-FEAR; FIG. 6P. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-085-FEAR and IgG1-5T4-085-FEAR; FIG. 6Q.Binding of bsIgG1-huCD3-H101G-FEALx5T4-127-FEAR and IgG1-5T4-127-FEAR;FIG. 6R. Binding of bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andIgG1-5T4-A1-FEAR; FIG. 6S. Binding ofbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR and IgG1-5T4-A3-FEAR.

FIGS. 7A-7C: Induction of cytotoxicity in vitro by CD3×5T4 bispecificantibodies in MDA-MB-231 cells using purified T cells as effector cells.MDA-MB-231 cells were incubated with increasing concentrations ofCD3×5T4 bispecific antibodies or monospecific, bivalent 5T4 antibodiesand isolated T cells as effector cells in an Effector:Target cell (E:T)ratio of 8:1. Purified T cells obtained from two different donors wereused for this experiment, donor A (left panels) and donor B (rightpanels). Cytotoxicity was determined by measuring the percentage ofviable MDA-MB-231 cells after 72 hrs of incubation (% viablecells=[absorbance sample−absorbance staurosporine-treated targetcells]/[absorbance untreated target cells−absorbancestaurosporine-treated target cells]×100). FIG. 7A. Cytotoxicity inducedin the presence of bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR and IgG1-5T4-207-FEAR; FIG. 7B.Cytotoxicity induced in the presence of bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEAR; FIG. 7C.Cytotoxicity induced in the presence of bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR.

FIG. 7D: IC50 values of cytotoxicity induced in vitro by CD3×5T4bispecific antibodies in MDA-MB-231 cells using purified T cells aseffector cells. IC50 values of the T-cell mediated cytotoxicity inducedby bsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-FEALx5T4-059-FEAR or bsIgG1-huCD3-H101G-FEALx5T4-059-FEARin MDA-MB-231 cells were analyzed using GraphPad Prism V7.02 software.Data are presented as mean IC50 values of two different donors±SD.

FIGS. 8A-8F: Induction of cytotoxicity by CD3×5T4 bispecific antibodiesin MDA-MB-231 cells using T cells as effector cells in vitro. MDA-MB-231cells were incubated with increasing concentrations of CD3×5T4bispecific antibodies or 5T4 homodimers and isolated T cells as effectorcells in an E:T ratio of 8:1. Three different donors were used for thisexperiment. Data shown are mean % survival±standard error of the mean(SEM) of three donors tested. FIG. 8A. T-cell-mediated cytotoxicity(decrease in survival) induced in the presence ofbsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andIgG1-5T4-207-FEAR; FIG. 8B. T-cell-mediated cytotoxicity induced in thepresence of bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR and IgG1-5T4-226-FEAR; FIG. 8C.T-cell-mediated cytotoxicity induced in the presence ofbsIgG1-huCD3-FEALx5T4-059-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andIgG1-5T4-059-FEAR; FIG. 8D. T-cell-mediated cytotoxicity induced in thepresence of bsIgG1-huCD3-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR and IgG1-5T4-106-FEAR; FIG. 8E.T-cell-mediated cytotoxicity induced in the presence ofbsIgG1-huCD3-FEALx5T4-A1-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andIgG1-5T4-A1-FEAR; FIG. 8F. T-cell-mediated cytotoxicity induced in thepresence of bsIgG1-huCD3-FEALx5T4-A3-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR and IgG1-5T4-A3-FEAR.

FIGS. 8G-8H: IC50 values of cytotoxicity induced by CD3×5T4 bispecificantibodies in MDA-MB-231 cells using T cells as effector cells in vitro.IC50 values of the T-cell-mediated cytotoxicity induced CD3×5T4bispecific antibodies in MDA-MB-231 cells were analyzed using GraphPadPrism V7.02 software. Data are presented as mean IC50 values of threedifferent donors±SD. FIG. 8G. IC50 values of the T-cell-mediatedcytotoxicity induced by bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR andbsIgG1-huCD3-FEALx5T4-A3-FEAR; FIG. 8H. IC50 values of theT-cell-mediated cytotoxicity induced bybsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR.

FIGS. 9A-9C: In vitro T-cell activation by CD3×5T4 bispecific antibodiesin the presence of MDA-MB-231 cells. MDA-MB-231 cells were incubatedwith increasing concentrations of CD3×5T4 bispecific antibodies andmonospecific, bivalent 5T4 antibodies, as indicated, and isolated Tcells as effector cells in an E:T ratio of 8:1. The expression of threeT cell activation markers (PD1 [upper panels], CD25 [middle panels] andCD69 [lower panels]) was analyzed by flow cytometry. Two differentdonors were used for this experiment, donor A (closed symbols) and donorB (open symbols). FIG. 9A. T-cell activation induced in the presence ofbsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andIgG1-5T4-207-FEAR; FIG. 9B. T-cell activation induced in the presence ofbsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR andIgG1-5T4-226-FEAR; FIG. 9C. T-cell activation induced in the presence ofbsIgG1-huCD3-FEALx5T4-059-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andIgG1-5T4-059-FEAR.

FIG. 9D: EC50 values of in vitro T-cell activation by CD3×5T4 bispecificantibodies in the presence of MDA-MB-231 cells. EC50 values of in vitroT-cell activation markers (PD1, CD25 and CD69) induced bybsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-FEALx5T4-059-FEAR or bsIgG1-huCD3-H101G-FEALx5T4-059-FEARin the presence of MDA-MB-231 cells were analyzed using GraphPad PrismV7.02 software. Data are presented as mean of two different donors±SD.

FIGS. 10A-10F: In vitro T-cell activation by CD3×5T4 bispecificantibodies in the presence of MDA-MB-231 cells. MDA-MB-231 cells wereincubated with increasing concentrations of CD3×5T4 bispecificantibodies and 5T4 homodimers and isolated T cells as effector cells inan E:T ratio of 8:1. T-cell activation was measured by an increase in %CD69+ cells within the CD4+(left panels) and CD8+(right panels) T cellpopulations. Three different donors were used for this experiment; datashown are mean % CD69 upregulation±SEM of three donors tested. FIG. 10A.T-cell activation induced in the presence ofbsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andIgG1-5T4-207-FEAR; FIG. 10B. T-cell activation induced in the presenceof bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEARand IgG1-5T4-226-FEAR; FIG. 10C. T-cell activation induced in thepresence of bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR and IgG1-5T4-059-FEAR; FIG. 10D.T-cell activation induced in the presence ofbsIgG1-huCD3-FEALx5T4-106-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR andIgG1-5T4-106-FEAR; FIG. 10E. T-cell activation induced in the presenceof bsIgG1-huCD3-FEALx5T4-A1-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-A1-FEARand IgG1-5T4-A1-FEAR; FIG. 10F. T-cell activation induced in thepresence of bsIgG1-huCD3-FEALx5T4-A3-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR and IgG1-5T4-A3-FEAR.

FIGS. 10G-10L: EC₅₀ values of in vitro T-cell activation by CD3×5T4bispecific antibodies in the presence of MDA-MB-231 cells. EC₅O valuesof T-cell activation markers (increase in % of CD69⁺[FIGS. 10G-10H],CD25+[FIGS. 101-10J] and PD1+[FIGS. 10K-10L], CD25 and CD69 cells withinthe CD4+ and CD8+ T cell populations) induced in vitro by CD3×5T4bispecific antibodies in the presence of MDA-MB-231 cells were analyzedusing GraphPad Prism V7.02 software. Data are presented as mean of threedifferent donors±SD. FIG. 10G. EC₅₀ values of the CD69 upregulationinduced by bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR andbsIgG1-huCD3-FEALx5T4-A3-FEAR; FIG. 10H. EC₅₀ values of the CD69upregulation induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR. FIG. 10I. EC₅₀ values of the CD25upregulation induced by bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR andbsIgG1-huCD3-FEALx5T4-A3-FEAR; FIG. 10J. EC₅₀ values of the CD25upregulation induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR. FIG. 10K. EC₅₀ values of the PD1upregulation induced by bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR andbsIgG1-huCD3-FEALx5T4-A3-FEAR; FIG. 10L. EC₅₀ values of the PD1upregulation induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR.

FIGS. 11A and 11B: T cell cytokine release induced by CD3×5T4 bispecificantibodies in the presence of 5T4-positive tumor cells. MDA-MB-231 cellswere incubated with 0.2 μg/mL CD3×5T4 bispecific antibodies(bsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-FEALx5T4-059-FEAR or bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR)and 5T4 monospecific antibodies (IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR orIgG1-5T4-059-FEAR) and isolated T cells as effector cells in an E:Tratio of 8:1. Release of cytokines was analyzed by U-PLEX assay. FIG.11A. Concentration of IL-10, IL-13 and TNF in the supernatant of T cell(derived from donor A)-tumor cell co-cultures, after 72 h of incubationwith CD3×5T4 bispecific antibodies or 5T4 monospecific antibodies. FIG.11B. Concentration of IL-10, IL-13 and TNF in the supernatant of T cell(derived from donor B)-tumor cell co-cultures, after 72 h of incubationwith CD3×5T4 bispecific antibodies or 5T4 monospecific antibodies.

FIGS. 12A and 12B: Induction of cytotoxicity in vitro by CD3×5T4bispecific antibodies in SK-OV-3 cells using PBMCs as effector cells atvarying E:T ratios. SK-OV-3 cells were incubated with increasingconcentrations of bsIgG1-huCD3-FEALx5T4-207-FEAR (left panels) orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (right panels) and PBMCs aseffector cells in an E:T ratio of 1:2, 1:1, 2:1, 4:1, 8:1 and 12:1.Cytotoxicity was determined by measuring the percentage of viableSK-OV-3 cells after 72 h of incubation (% viable cells=[absorbancesample−absorbance staurosporine-treated target cells]/[absorbanceuntreated target cells−absorbance staurosporine-treated targetcells]×100). PBMCs from two different donors were used for thisexperiment: FIG. 12A. donor C and FIG. 12B. donor D.

FIGS. 13A and 13B: Induction of cytotoxicity in SK-OV-3 cells in vitroby CD3×5T4 bispecific antibodies using T cells as effector cells atvarying E:T ratios. SK-OV-3 cells were incubated with increasingconcentrations of bsIgG1-huCD3-FEALx5T4-207-FEAR (left panels) orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (right panels) and isolated T cellsas effector cells in an E:T ratio of 1:2, 1:1, 2:1, 4:1 and 8:1. Theefficiency of cytotoxicity was determined by measuring the percentage ofviable SK-OV-3 cells after 72 h of incubation (% viablecells=[absorbance sample−absorbance staurosporine-treated targetcells]/[absorbance untreated target cells−absorbancestaurosporine-treated target cells]×100). T cells from two differentdonors were used for this experiment: FIG. 13A. donor E and FIG. 13B.donor F.

FIGS. 14A and 14B: Anti-tumor activity of CD3×5T4 bispecific antibodiesin a MDA-MB-231 xenograft model in NSG-HIS mice. FIG. 14A. Average tumorsize in the MDA-MB-231 xenograft model in NSG-HIS mice after treatmentwith PBS (vehicle control), 0.5 mg/kg bsIgG1-huCD3-FEALx5T4-207-FEAR or0.5 mg/kg bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR. Tumor size was assessedby caliper measurement. Error bars indicate SEM. FIG. 14B. Percentage ofNSG-HIS mice injected with MDA-MB-231 cells with a tumor size <500 mm³after treatment with PBS, bsIgG1-huCD3-FEALx5T4-207-FEAR orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR.

FIGS. 15A-15D: Binding of directly FITC-labeled 5T4-specific antibodiesto human 5T4 variants with single alanine mutations at positions 32 to355 of human 5T4 ECD, as determined by flow cytometry. Binding wasexpressed as Z-score (fold change), as a measure for change in bindingcompared to a non-cross blocking 5T4-specific control antibody(bsIgG1-5T4-A1-F405Lxb12-FEAR-FITC) used for normalization. The numberon the x-axis refers to the amino acid positions in human 5T4 (SEQ ID:1). Residues where the Z-score in binding was lower than −1.5 (indicatedby the dotted line) were considered ‘loss of binding mutants’. Residueswith a positive Z-score in binding are loss of binding residues for thenon-cross blocking 5T4 specific control antibody(bsIgG1-5T4-A1-67F-F405Lxb12-FEAR-FITC). Residues on aa position 38, 45,49, 51, 54, 62, 64, 66, 68, 71, 72, 77, 91, 104, 108, 110, 112, 118,121, 122, 135, 137, 155, 161, 167, 171, 201, 202, 205, 208, 218, 231,269, 279, 298, 300, 303, 323, 324, 340 and 344 were not evaluated, asthese positions contained either endogenous alanines or cysteines. Datashown are Z-scores for binding of (FIG. 15A)bsIgG1-b12-FEALx5T4-059-FEAR-FITC, (FIG. 15B)bsIgG1-b12-FEALx5T4-207-FEAR-FITC, (FIG. 15C)bsIgG1-b12-FEALx5T4-226-FEAR-FITC, and (FIG. 15D)bsIgG1-5T4-A3-F405Lxb12-FEAR-FITC. Buried residues with a Z-score justbelow −1.5 that were predicted to be spatially separated from themajority of surface-exposed loss of binding residues were excluded (forbIgG1-b12-FEALx5T4-207-FEAR-FITC: L281 [Z-score: −1.57] and P326[Z-score: −1.54]; and for bsIgG1-b12-FEALx5T4-226-FEAR-FITC: L273[Z-score: −1.58], L281 [Z-score: −1.65], N294 [Z-score: −1.57], L309[Z-score: −1.63] and P326 [Z-score: −1.67]).

FIGS. 16A and 16B: Induction of cytotoxicity in vitro by CD3×5T4bispecific antibodies in tumor cells of different indications using Tcells as effector cells. Tumor cells were incubated with increasingconcentrations of bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR or controlantibodies (bsIgG1-huCD3-H101G-FEALxb12-FEAR,bsIgG1-b12-FEALx5T4-207-FEAR) and isolated T cells as effector cells inan E:T ratio of 4:1. Cytotoxicity (decrease in survival) was determinedby measuring the percentage of viable tumor cells after 72 h ofincubation. Data shown are mean % survival±SEM of duplicate wells fromone representative donor out of at least three donors tested. FIG. 16A.Cytotoxicity (decrease in survival) induced in pancreas cancer celllines; FIG. 16B. Cytotoxicity (decrease in survival) induced in cervicalcancer cell lines.

FIG. 16C: IC50 values of cytotoxicity induced in vitro by CD3×5T4bispecific antibodies in tumor cell lines of different indications usingT cells as effector cells. IC50 values of the T-cell-mediatedcytotoxicity induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR in tumorcells of the indicated indications were analyzed using GraphPad PrismV7.02 software. Data are presented as mean IC50 values of at least threedifferent donors (see Table 10)±SD.

FIGS. 17A-17D: In vitro T-cell activation by CD3×5T4 bispecificantibodies in the presence of tumor cells of different indications.Tumor cells were incubated with increasing concentrations ofbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR or control antibodies(bsIgG1-huCD3-H101G-FEALxb12-FEAR, bsIgG1-b12-FEALx5T4-207-FEAR andisolated T cells as effector cells in an E:T ratio of 4:1 for 72 h.T-cell activation was measured by the upregulation of CD69 (% of CD69+cells) within CD4⁺ (left panels) and CD8⁺ (right panels) T-cellpopulations. Data shown are mean % CD69+ cells±SD of duplicate wellsfrom one representative donor out of at least three donors tested. FIG.17A. T-cell activation induced by CD3×5T4 bispecific antibodies in thepresence of pancreas cancer cell line BxPc-3; FIG. 17B. T-cellactivation induced by CD3×5T4 bispecific antibodies in the presence ofpancreas cancer cell line PANC-1; FIG. 17C. T-cell activation induced byCD3×5T4 bispecific antibodies in the presence of cervical cancer cellline SiHa; FIG. 17D. T-cell activation induced by CD3×5T4 bispecificantibodies in the presence of cervical cancer cell line Ca Ski.

FIGS. 17E-17F: EC50 values of in vitro T-cell activation by CD3×5T4bispecific antibodies in with the presence of tumor cell lines ofdifferent indications. EC50 values of the T-cell activation (% of CD69+cells within CD4⁺ and CD8⁺ T-cell populations) induced bybsIgG1-huCD3-H101G-FEALx5T4-207-FEAR in co-culture with tumor cell linesof the different indications were analyzed using GraphPad Prism V7.02software. Data are presented as mean EC50 values of at least threedifferent donors (see Table 10)±SD. FIG. 17E. EC50 values of CD4+ T-cellactivation induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR in thepresence of the indicated tumor cell lines; FIG. 17F. EC50 values ofCD8+ T-cell activation induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEARin the presence of the indicated tumor cell lines.

DETAILED DESCRIPTION Definitions

The term “antibody” as used herein is intended to refer to animmunoglobulin molecule, a fragment of an immunoglobulin molecule, or aderivative of either thereof, which has the ability to specifically bindto an antigen under typical physiological and/or tumor-specificconditions with a half-life of significant periods of time, such as atleast about 30 minutes, at least about 45 minutes, at least about onehour, at least about two hours, at least about four hours, at leastabout 8 hours, at least about 12 hours, at least about 24 hours or more,at least about 48 hours or more, at least about 3, 4, 5, 6, 7 or moredays, etc., or any other relevant functionally-defined period (such as atime sufficient to induce, promote, enhance, and/or modulate aphysiological response associated with antibody binding to the antigenand/or time sufficient for the antibody to be internalized). The bindingregion (or binding domain which may be used herein, both having the samemeaning) which interacts with an antigen, comprises variable regions ofboth the heavy and light chains of the immunoglobulin molecule. Theconstant regions of the antibodies (Abs) may mediate the binding of theimmunoglobulin to host tissues or factors, including various cells ofthe immune system (such as effector cells) and components of thecomplement system such as C1q, the first component in the classicalpathway of complement activation.

In the context of the present invention, the term “antibody” includes amonoclonal antibody (mAb), an antibody-like polypeptide, such as achimeric antibody and a humanized antibody, as well as an ‘antibodyfragment’ or a ‘fragment thereof’ retaining the ability to specificallybind to the antigen (antigen-binding fragment) provided by any knowntechnique, such as enzymatic cleavage, peptide synthesis, andrecombinant techniques, and retaining the ability to be conjugated to atoxin. An antibody as defined according to the invention can possess anyisotype unless the disclosure herein is otherwise limited.

As indicated above, the term antibody as used herein, unless otherwisestated or clearly contradicted by context, includes fragments of anantibody that retain the ability to specifically interact, such as bind,to the antigen. It has been shown that the antigen-binding function ofan antibody may be performed by fragments of a full-length antibody.Examples of binding fragments encompassed within the term “antibody”include (i) a Fab′ or Fab fragment, a monovalent fragment consisting ofthe light chain variable domain (VL), heavy chain variable domain (VH),light chain constant region (CL) and heavy chain constant region domain1 (CH1) domains, or a monovalent antibody as described in WO2007/059782; (ii) F(ab′)₂ fragments, bivalent fragments comprising twoFab fragments linked by a disulfide bridge at the hinge region; (iii) anFd fragment consisting essentially of the VH and CH1 domains; (iv) an Fvfragment consisting essentially of the VL and VH domains of a single armof an antibody, (v) a dAb fragment Ward et al., Nature 341, 544-546(1989), which consists essentially of a VH domain and is also calleddomain antibody Holt et al; Trends Biotechnol. 2003 November;21(11):484-90; (vi) camelid or nanobodies Revets et al; Expert Opin BiolTher. 2005 January; 5(1):111-24 and (vii) an isolated complementaritydetermining region (CDR). Furthermore, although the two domains of theFv fragment, VL and VH, are coded for by separate genes, they may bejoined, using recombinant methods, by a synthetic linker that enablesthem to be made as a single protein chain in which the VL and VH regionspair to form monovalent molecules (known as single chain antibodies orsingle chain Fv (scFv), see for instance Revets et al; Expert Opin BiolTher. 2005 January; 5(1):111-24 and Bird et al., Science 242, 423-426(1988). Such single chain antibodies are encompassed within the termantibody unless otherwise noted or clearly indicated by context.Although such fragments are generally included within the meaning ofantibody, they collectively and each independently are unique featuresof the present invention, exhibiting different biological properties andutility. These and other useful antibody fragments in the context of thepresent invention are discussed further herein.

An antibody can be produced in and collected from different in vitro orex vivo expression or production systems, for example from recombinantlymodified host cells, from hybridomas or systems that use cellularextracts supporting in vitro transcription and/or translation of nucleicacid sequences encoding the antibody. It is to be understood that amultitude of different antibodies, the antibodies being as defined inthe context of the present invention, is one that can be provided byproducing each antibody separately in a production system as mentionedabove and thereafter mixing the antibodies, or by producing severalantibodies in the same production system.

The term “immunoglobulin heavy chain” or “heavy chain of animmunoglobulin” as used herein is intended to refer to one of the heavychains of an immunoglobulin. A heavy chain is typically comprised of aheavy chain variable region (abbreviated herein as VH) and a heavy chainconstant region (abbreviated herein as CH) which defines the isotype ofthe immunoglobulin. The heavy chain constant region typically iscomprised of three domains, CH1, CH2, and CH3. The term “immunoglobulin”as used herein is intended to refer to a class of structurally relatedglycoproteins consisting of two pairs of polypeptide chains, one pair oflight (L) low molecular weight chains and one pair of heavy (H) chains,all four potentially inter-connected by disulfide bonds. The structureof immunoglobulins has been well characterized (see for instanceFundamental Immunology Ch. 7 (Paul, W., ed., 2nd ed. Raven Press, N.Y.(1989)). Within the structure of the immunoglobulin, the two heavychains are inter-connected via disulfide bonds in the so-called “hingeregion”. Equally to the heavy chains, each light chain is typicallycomprised of several regions; a light chain variable region (abbreviatedherein as VL) and a light chain constant region. The light chainconstant region typically is comprised of one domain, CL. Furthermore,the VH and VL regions may be further subdivided into regions ofhypervariability (or hypervariable regions which may be hypervariable insequence and/or form of structurally defined loops), also termedcomplementarity determining regions (CDRs), interspersed with regionsthat are more conserved, termed framework regions (FRs). Each VH and VLis typically composed of three CDRs and four FRs, arranged fromamino-terminus to carboxy-terminus in the following order: FR1, CDR1,FR2, CDR2, FR3, CDR3, FR4. CDR sequences are defined according to IMGT(see Lefranc M P. et al., Nucleic Acids Research, 27, 209-212, 1999] andBrochet X. Nucl. Acids Res. 36, W503-508 (2008)).

When used herein, the terms “half molecule”, “Fab-arm” and “arm” referto one heavy chain-light chain pair. When a bispecific antibody isdescribed to comprise a half-molecule antibody “derived from” a firstantibody, and a half-molecule antibody “derived from” a second antibody,the term “derived from” indicates that the bispecific antibody wasgenerated by recombining, by any known method, said half-molecules fromeach of said first and second antibodies into the resulting bispecificantibody. In this context, “recombining” is not intended to be limitedby any particular method of recombining and thus includes all of themethods for producing bispecific antibodies described herein below,including for example recombining by half-molecule exchange, as well asrecombining at nucleic acid level and/or through co-expression of twohalf-molecules in the same cells.

The term “antigen-binding region” or “binding region” as used herein,refers to a region of an antibody which is capable of binding to theantigen. The antigen can be any molecule, such as a polypeptide, e.g.present on a cell, bacterium, or virion. The terms “antigen” and“target” may, unless contradicted by the context, be usedinterchangeably in the context of the present invention. The terms“antigen-binding region” and “antigen-binding site” may, unlesscontradicted by the context, be used interchangeably in the context ofthe present invention.

The term “blocks binding” or “blocking the binding of an antibody” or“cross-blocking binding” or “cross-blocks binding” refers to thesituation where one antibody bound to a specific antigen preventsbinding of the second antibody to the same antigen and vice versa. Inthe absence of the other antibody, each antibody has the ability to bindto the antigen as determined by a significant binding response, whereasone of the antibodies lacks a binding response when the other antibodyis present. The ability of one antibody to block the binding of anotherantibody may be determined by biolayer interferometry in a classicalsandwich epitope binning assay format, for instance as described inExample 3 in the present application and by Abdiche et al. (Abdiche Y N,Malashock D S, Pinkerton A, Pons J. Exploring blocking assays usingOctet, ProteOn, and Biacore biosensors. Anal Biochem. 2009; 386(2):172-180). Briefly, in a sandwich epitope binning assay, an antibody insolution is tested for binding to its specific antigen that is firstcaptured via an immobilized antibody. In the context of the presentinvention, one antibody does not block the binding of another antibodyif it is capable of “displacing” the other antibody, according to thedefinition of “displacement” below. The terms “blocks binding” and“blocking the binding of an antibody” and “cross-blocking binding” and“cross-blocks binding” may, unless contradicted by the context, be usedinterchangeably in the context of the present invention. Preferably, theability of one antibody to block the binding of another antibody isdetermined using full-length antibodies.

The term “displacement” or “ability to displace” or “displacing” refersto the situation wherein two antibodies perturb one another's binding toan antigen by kinetically altering one another's binding to theirspecific antigen via the formation of a transient trimolecular complex,which rapidly collapses by retaining one antibody to the antigen anddisplacing the other. Antibody displacement is defined in Abdiche etal., 2017 (Abdiche Y N, Yeung A Y, Ni I, Stone D, Miles A, Morishige W,et al. (2017) Antibodies Targeting Closely Adjacent or MinimallyOverlapping Epitopes Can Displace One Another. PLoS ONE 12(1): e0169535.doi:10.1371/journal.pone.0169535). Antibody displacement may bedetermined by biolayer interferometry using real-time label-freebiosensors in a classical sandwich assay format as described in Abdicheet al. 2017 and Example 4 in the present application. Preferably,antibody displacement is determined using antibodies which are in theIgG format.

The term “binding” as used herein refers to the binding of an antibodyto a predetermined antigen or target, typically with a binding affinitycorresponding to a K_(D) of 1E⁻⁶ M or less, e.g. 5E⁻⁷ M or less, 1E⁻⁷ Mor less, such as 5E⁻⁸ M or less, such as 1E⁻⁸ M or less, such as 5E M orless, or such as 1E M or less, when determined by biolayerinterferometry using the antibody as the ligand and the antigen as theanalyte and binds to the predetermined antigen with an affinitycorresponding to a K_(D) that is at least ten-fold lower, such as atleast 100-fold lower, for instance at least 1,000-fold lower, such as atleast 10,000-fold lower, for instance at least 100,000-fold lower thanits affinity for binding to a non-specific antigen (e.g., BSA, casein)other than the predetermined antigen or a closely-related antigen.

The term “K_(D)” (M), as used herein, refers to the dissociationequilibrium constant of a particular antibody-antigen interaction, andis obtained by dividing k_(d) by k_(a).

The term “k_(d)” (sec⁻¹), as used herein, refers to the dissociationrate constant of a particular antibody-antigen interaction. Said valueis also referred to as the k_(off) value or off-rate.

The term “k_(a)” (M⁻¹×sec⁻¹), as used herein, refers to the associationrate constant of a particular antibody-antigen interaction. Said valueis also referred to as the k_(off) value or on-rate.

The term “5T4” as used herein, refers to the protein entitled 5T4, whichis also referred to as trophoblast glycoprotein, 5T4 oncofetal antigen,5T4 oncofetal trophoblast glycoprotein, TPBG, WAIF1 and M6P1. It is72-80 kDa transmembrane protein with an extensively N-linkedglycosylated core. In humans (Homo sapiens), the 5T4 protein has theamino acid sequence shown in SEQ ID NO: 1 (Human Trophoblastglycoprotein: Uniprot accession no. Q13641). In the amino acid sequenceshown in SEQ ID NO: 1, amino acid residues 1-31 are a signal peptide,and amino acid residues 32-420 are the mature polypeptide. In cynomolgusmonkey (Macaca fascicularis), the 5T4 protein has the amino acidsequence shown in SEQ ID NO: 2 (Uniprot accession no. Q4R8Y9). In theamino acid sequence shown in SEQ ID NO: 2, amino acid residues 1-34 area signal peptide, and amino acid residues 35-420 are the maturepolypeptide. In chicken (Gallus gallus), the 5T4 protein has the aminoacid sequence shown in SEQ ID NO: 3 (Uniprot accession no. R4GM46). Inthe sequence shown in SEQ ID NO: 3, amino acid residues 1-27 are asignal peptide, and amino acid residues 28-379 are the maturepolypeptide.

The term “CD3” as used herein, refers to the human Cluster ofDifferentiation 3 protein which is part of the T-cell co-receptorprotein complex and is composed of four distinct chains. CD3 is alsofound in other species, and thus, the term “CD3” is not limited to humanCD3 unless contradicted by context. In mammals, the complex contains aCD3γ (gamma) chain (human CD3γ chain UniProtKB/Swiss-Prot No P09693, orcynomolgus monkey CD3γ UniProtKB/Swiss-Prot No Q95LI7), a CD36 (delta)chain (human CD36 UniProtKB/Swiss-Prot No P04234, or cynomolgus monkeyCD36 UniProtKB/Swiss-Prot No Q95LI8), two CD3E (epsilon) chains (humanCD3E UniProtKB/Swiss-Prot No P07766; amino acid residues 1-22 is asignal peptide and amino acid residues 23-207 is the mature CD3Epolypeptide, which is identified herein as SEQ ID NO: 4; cynomolgusmonkey CD3E UniProtKB/Swiss-Prot No Q95L15; or rhesus monkey CD3EUniProtKB/Swiss-Prot No G7NCB9), and a CD3-chain (zeta) chain (human CD3UniProtKB/Swiss-Prot No P20963, cynomolgus monkey CD3UniProtKB/Swiss-Prot No Q09TK0). These chains associate with a moleculeknown as the T-cell receptor (TCR) and generate an activation signal inT lymphocytes. The TCR and CD3 molecules together comprise the TCRcomplex.

The term “antibody binding region” refers to a region of the antigen,which comprises the epitope to which the antibody binds. An antibodybinding region may be determined by epitope binning using biolayerinterferometry, by alanine scan, or by shuffle assays (using antigenconstructs in which regions of the antigen are exchanged with that ofanother species and determining whether the antibody still binds to theantigen or not). The amino acids within the antibody binding region thatare involved in the interaction with the antibody may be determined byhydrogen/deuterium exchange mass spectrometry and by crystallography ofthe antibody bound to its antigen.

The term “epitope” means an antigenic determinant which is specificallybound by an antibody. Epitopes usually consist of surface groupings ofmolecules such as amino acids, sugar side chains or a combinationthereof and usually have specific three dimensional structuralcharacteristics, as well as specific charge characteristics.Conformational and non-conformational epitopes are distinguished in thatthe binding to the former but not the latter is lost in the presence ofdenaturing solvents. The epitope may comprise amino acid residues whichare directly involved in the binding, and other amino acid residues,which are not directly involved in the binding, such as amino acidresidues which are effectively blocked or covered by the antibody whenit is bound to the antigen (in other words, the amino acid residue iswithin or closely adjacent to the footprint of the specific antibody).

The terms “monoclonal antibody”, “monoclonal Ab”, “monoclonal antibodycomposition”, “mAb”, or the like, as used herein refer to a preparationof antibody molecules of single molecular composition. A monoclonalantibody composition displays a single binding specificity and affinityfor a particular epitope. Accordingly, the term “human monoclonalantibody” refers to antibodies displaying a single binding specificitywhich have variable and constant regions derived from human germlineimmunoglobulin sequences. The human monoclonal antibodies may beproduced by a hybridoma which includes a B cell obtained from atransgenic or transchromosomal non-human animal, such as a transgenicmouse, having a genome comprising a human heavy chain transgene and alight chain transgene, fused to an immortalized cell. Monoclonalantibodies may also be produced from recombinantly modified host cells,or systems that use cellular extracts supporting in vitro transcriptionand/or translation of nucleic acid sequences encoding the antibody.

The term “isotype” as used herein refers to the immunoglobulin class(for instance IgG1, IgG2, IgG3, IgG4, IgD, IgA, IgE, or IgM) or anyallotypes thereof, such as IgG1m(za) and IgG1m(f)) that is encoded byheavy chain constant region genes. Further, each heavy chain isotype canbe combined with either a kappa (κ) or lambda (λ) light chain.

The term “full-length antibody” when used herein, refers to an antibody(e.g., a parent or variant antibody) comprising one or two pairs ofheavy and light chains, each containing all heavy and light chainconstant and variable domains that are normally found in a heavychain-light chain pair of a wild-type antibody of that isotype. In afull length variant antibody, the heavy and light chain constant andvariable domains may in particular contain amino acid substitutions thatimprove the functional properties of the antibody when compared to thefull length parent or wild type antibody. A full-length antibodyaccording to the present invention may be produced by a methodcomprising the steps of (i) cloning the CDR sequences into a suitablevector comprising complete heavy chain sequences and complete lightchain sequence, and (ii) expressing the complete heavy and light chainsequences in suitable expression systems. It is within the knowledge ofthe skilled person to produce a full-length antibody when starting outfrom either CDR sequences or full variable region sequences. Thus, theskilled person would know how to generate a full-length antibodyaccording to the present invention.

The term “human antibody”, as used herein, is intended to includeantibodies having variable and framework regions derived from humangermline immunoglobulin sequences and a human immunoglobulin constantdomain. The human antibodies of the invention may include amino acidresidues not encoded by human germline immunoglobulin sequences (e.g.,mutations, insertions or deletions introduced by random or site-specificmutagenesis in vitro or by somatic mutation in vivo). However, the term“human antibody”, as used herein, is not intended to include antibodiesin which CDR sequences derived from the germline of another non-humanspecies, such as a mouse, have been grafted onto human frameworksequences.

The term “humanized antibody” as used herein, refers to a geneticallyengineered non-human antibody, which contains human antibody constantdomains and non-human variable domains modified to contain a high levelof sequence homology to human variable domains. This can be achieved bygrafting of the six non-human antibody complementarity-determiningregions (CDRs), which together form the antigen binding site, onto ahomologous human acceptor framework region (FR) (see WO92/22653 andEP0629240). In order to fully reconstitute the binding affinity andspecificity of the parental antibody, the substitution of frameworkresidues from the parental antibody (i.e. the non-human antibody) intothe human framework regions (back-mutations) may be required. Structuralhomology modeling may help to identify the amino acid residues in theframework regions that are important for the binding properties of theantibody. Thus, a humanized antibody may comprise non-human CDRsequences, primarily human framework regions optionally comprising oneor more amino acid back-mutations to the non-human amino acid sequence,and fully human constant regions. Optionally, additional amino acidmodifications, which are not necessarily back-mutations, may be appliedto obtain a humanized antibody with preferred characteristics, such asaffinity and biochemical properties.

The term “Fc region” as used herein, refers to a region comprising, inthe direction from the N- to C-terminal end of the antibody, at least ahinge region, a CH2 region and a CH3 region. An Fc region of theantibody may mediate the binding of the immunoglobulin to host tissuesor factors, including various cells of the immune system (such aseffector cells) and components of the complement system.

The term “hinge region” as used herein refers to the hinge region of animmunoglobulin heavy chain. Thus, for example the hinge region of ahuman IgG1 antibody corresponds to amino acids 216-230 according to theEu numbering as set forth in Kabat Kabat, E. A. et al., Sequences ofproteins of immunological interest. 5th Edition—US Department of Healthand Human Services, NIH publication No. 91-3242, pp 662,680, 689 (1991).However, the hinge region may also be any of the other subtypes asdescribed herein.

The term “CH1 region” or “CH1 domain” as used herein refers to the CH1region of an immunoglobulin heavy chain. Thus, for example the CH1region of a human IgG1 antibody corresponds to amino acids 118-215according to the Eu numbering as set forth in Kabat (ibid). However, theCH1 region may also be any of the other subtypes as described herein.

The term “CH2 region” or “CH2 domain” as used herein refers to the CH2region of an immunoglobulin heavy chain. Thus, for example the CH2region of a human IgG1 antibody corresponds to amino acids 231-340according to the Eu numbering as set forth in Kabat (ibid). However, theCH2 region may also be any of the other subtypes as described herein.

The term “CH3 region” or “CH3 domain” as used herein refers to the CH3region of an immunoglobulin heavy chain. Thus for example the CH3 regionof a human IgG1 antibody corresponds to amino acids 341-447 according tothe Eu numbering as set forth in Kabat (ibid). However, the CH3 regionmay also be any of the other subtypes as described herein.

The term “Fc-mediated effector functions,” as used herein, is intendedto refer to functions that are a consequence of binding a polypeptide orantibody to its target or antigen on a cell membrane wherein theFc-mediated effector function is attributable to the Fc region of thepolypeptide or antibody. Examples of Fc-mediated effector functionsinclude (i) C1q binding, (ii) complement activation, (iii)complement-dependent cytotoxicity (CDC), (iv) antibody-dependentcell-mediated cytotoxity (ADCC), (v) Fc-gamma receptor (FcgR)-binding,(vi) antibody-dependent, FcγR-mediated antigen crosslinking, (vii)antibody-dependent cellular phagocytosis (ADCP), (viii)complement-dependent cellular cytotoxicity (CDCC), (ix)complement-enhanced cytotoxicity, (x) binding to complement receptor ofan opsonized antibody mediated by the antibody, (xi) opsonisation, and(xii) a combination of any of (i) to (xi).

The term “inertness”, “inert” or “non-activating” as used herein, refersto an Fc region which is at least not able to bind any FcγR, induceFc-mediated cross-linking of FcγRs, or induce FcγR-mediatedcross-linking of target antigens via two Fc regions of individualantibodies, or is not able to bind C1q. The inertness of an Fc region ofan antibody, may be tested using the antibody in a monospecific orbispecific format.

The term “full-length” when used in the context of an antibody indicatesthat the antibody is not a fragment, but contains all of the domains ofthe particular isotype normally found for that isotype in nature, e.g.the VH, CH1, CH2, CH3, hinge, VL and CL domains for an IgG1 antibody.

The term “monovalent antibody”, in the context of the present invention,refers to an antibody molecule that can interact with a specific epitopeon an antigen, with only one antigen binding domain (e.g. one Fab arm).In the context of a bispecific antibody, “monovalent antibody binding”refers to the binding of the bispecific antibody to one specific epitopeon an antigen with only one antigen binding domain (e.g. one Fab arm).

The term “monospecific antibody” in the context of the presentinvention, refers to an antibody that has binding specificity to oneepitope only. The antibody may be a monospecific, monovalent antibody(i.e. carrying only one antigen binding region) or a monospecifc,bivalent antibody (i.e. an antibody with two identical antigen bindingregions).

The term “bispecific antibody” refers to an antibody having twonon-identical antigen binding domains, e.g. two non-identical Fab-armsor two Fab-arms with non-identical CDR regions. In the context of thisinvention, bispecific antibodies have specificity for at least twodifferent epitopes. Such epitopes may be on the same or differentantigens or targets. If the epitopes are on different antigens, suchantigens may be on the same cell or different cells, cell types orstructures, such as extracellular matrix or vesicles and solubleprotein. A bispecific antibody may thus be capable of crosslinkingmultiple antigens, e.g. two different cells.

The term “bivalent antibody” refers to an antibody that has two antigenbinding regions, which bind to epitopes on one or two targets orantigens or binds to one or two epitopes on the same antigen. Hence, abivalent antibody may be a monospecific, bivalent antibody or abispecific, bivalent antibody. The term “amino acid” and “amino acidresidue” may herein be used interchangeably, and are not to beunderstood limiting. Amino acids are organic compounds containing amine(—NH₂) and carboxyl (—COOH) functional groups, along with a side chain(R group) specific to each amino acid. In the context of the presentinvention, amino acids may be classified based on structure and chemicalcharacteristics. Thus, classes of amino acids may be reflected in one orboth of the following tables:

Main classification based on structure and general chemicalcharacterization of R group

Class Amino acid Acidic Residues D and E Basic Residues K, R, and HHydrophilic Uncharged Residues S, T, N, and Q Aliphatic UnchargedResidues G, A, V, L, and I Non-polar Uncharged Residues C, M, and PAromatic Residues F, Y, and W

Alternative Physical and Functional Classifications of Amino AcidResidues

Class Amino acid Hydroxyl group containing residues S and T Aliphaticresidues I, L, V, and M Cycloalkenyl-associated residues F, H, W, and YHydrophobic residues A, C, F, G, H, I, L, M, R, T, V, W, and YNegatively charged residues D and E Polar residues C, D, E, H, K, N, Q,R, S, and T Positively charged residues H, K, and R Small residues A, C,D, G, N, P, S, T, and V Very small residues A, G, and S Residuesinvolved in turn formation A, C, D, E, G, H, K, N, Q, R, S, P, and TFlexible residues Q, T, K, S, G, P, D, E, and R

Substitution of one amino acid for another may be classified as aconservative or non-conservative substitution. In the context of theinvention, a “conservative substitution” is a substitution of one aminoacid with another amino acid having similar structural and/or chemicalcharacteristics, such substitution of one amino acid residue for anotheramino acid residue of the same class as defined in any of the two tablesabove: for example, leucine may be substituted with isoleucine as theyare both aliphatic, branched hydrophobes. Similarly, aspartic acid maybe substituted with glutamic acid since they are both small, negativelycharged residues.

In the context of the present invention, a substitution in an antibodyis indicated as:

-   -   Original amino acid-position-substituted amino acid;

Referring to the well-recognized nomenclature for amino acids, the threeletter code, or one letter code, is used, including the codes “Xaa” or“X” to indicate any amino acid residue. Thus, Xaa or X may typicallyrepresent any of the 20 naturally occurring amino acids. The term“naturally occurring” as used herein refers to any one of the followingamino acid residues; glycine, alanine, valine, leucine, isoleucine,serine, threonine, lysine, arginine, histidine, aspartic acid,asparagine, glutamic acid, glutamine, proline, tryptophan,phenylalanine, tyrosine, methionine, and cysteine. Accordingly, thenotation “K409R” or “Lys409Arg” means, that the antibody comprises asubstitution of Lysine with Arginine in amino acid position 409.

Substitution of an amino acid at a given position to any other aminoacid is referred to as:

Original amino acid—position; or e.g. “K409”

For a modification where the original amino acid(s) and/or substitutedamino acid(s) may comprise more than one, but not all amino acid(s), themore than one amino acid may be separated by “,” or “/”. E.g. thesubstitution of Lysine with Arginine, Alanine, or Phenylalanine inposition 409 is: “Lys409Arg, Ala, Phe” or “Lys409Arg/Ala/Phe” or “K409R,A, F” or “K409R/A/F” or “K409 to R, A, or F”.

Such designation may be used interchangeably in the context of theinvention but have the same meaning and purpose.

Furthermore, the term “a substitution” embraces a substitution into anyone or the other nineteen natural amino acids, or into other aminoacids, such as non-natural amino acids. For example, a substitution ofamino acid K in position 409 includes each of the followingsubstitutions: 409A, 409C, 409D, 409E, 409F, 409G, 409H, 409I, 409L,409M, 409N, 4090, 409R, 409S, 409T, 409V, 409W, 409P, and 409Y. This is,by the way, equivalent to the designation 409X, wherein the X designatesany amino acid other than the original amino acid. These substitutionsmay also be designated K409A, K409C, etc. or K409A,C, etc. orK409A/C/etc. The same applies by analogy to each and every positionmentioned herein, to specifically include herein any one of suchsubstitutions.

The antibody according to the invention may also comprise a deletion ofan amino acid residue. Such deletion may be denoted “del”, and includes,e.g., writing as K409del. Thus, in such embodiments, the Lysine inposition 409 has been deleted from the amino acid sequence.

The term “host cell”, as used herein, is intended to refer to a cellinto which an expression vector has been introduced. It should beunderstood that such terms are intended to refer not only to theparticular subject cell, but also to the progeny of such a cell. Becausecertain modifications may occur in succeeding generations due to eithermutation or environmental influences, such progeny may not, in fact, beidentical to the parent cell, but are still included within the scope ofthe term “host cell” as used herein. Recombinant host cells include, forexample, transfectomas, such as CHO cells, HEK-293 cells, Expi293Fcells, PER.C6 cells, NS0 cells, and lymphocytic cells, and prokaryoticcells such as E. coli and other eukaryotic hosts such as plant cells andfungi.

The term “transfectoma”, as used herein, includes recombinant eukaryotichost cells expressing the antibody or a target antigen, such as CHOcells, PER.C6 cells, NS0 cells, HEK-293 cells, Expi293F cells, plantcells, or fungi, including yeast cells.

For purposes of the present invention, the sequence identity between twoamino acid sequences is determined using the Needleman-Wunsch algorithm(Needleman and Wunsch, 1970, J. Mol. Biol. 48: 443-453) as implementedin the Needle program of the EMBOSS package (EMBOSS: The EuropeanMolecular Biology Open Software Suite, Rice et al., 2000, Trends Genet.16: 276-277), preferably version 5.0.0 or later. The parameters used aregap open penalty of 10, gap extension penalty of 0.5, and the EBLOSUM62(EMBOSS version of BLOSUM62) substitution matrix. The output of Needlelabeled “longest identity” (obtained using the -nobrief option) is usedas the percent identity and is calculated as follows:(Identical Residues×100)/(Length of Alignment−Total Number of Gaps inAlignment).

The retention of similar residues may also or alternatively be measuredby a similarity score, as determined by use of a BLAST program (e.g.,BLAST 2.2.8 available through the NCBI using standard settings BLOSUM62,Open Gap=11 and Extended Gap=1). Suitable variants typically exhibit atleast about 45%, such as at least about 55%, at least about 65%, atleast about 75%, at least about 85%, at least about 90%, at least about95%, or more (e.g., about 99%) similarity to the parent sequence.

The term “internalized” or “internalization” as used herein, refers to abiological process in which molecules such as the antibody according tothe present invention, are engulfed by the cell membrane and drawn intothe interior of the cell. Internalization may also be referred to as“endocytosis”.

Antibodies

In a first aspect, the present invention provides an antibody comprisingat least one antigen-binding region capable of binding to 5T4(Trophoblast glycoprotein), wherein the antibody is able to blockbinding to 5T4 of an antibody selected from the group consisting of:

-   -   a) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 5 and a VL region comprising the        sequence set forth in SEQ ID NO: 9 [059],    -   b) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 12 and a VL region comprising the        sequence set forth in SEQ ID NO: 16 [076],    -   c) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 19 and a VL region comprising the        sequence set forth in SEQ ID NO: 23 [085],    -   d) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 26 and a VL region comprising the        sequence set forth in SEQ ID NO: 30 [106],    -   e) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 33 and a VL region comprising the        sequence set forth in SEQ ID NO: 37 [127],    -   f) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 40 and a VL region comprising the        sequence set forth in SEQ ID NO: 44 [207]; and    -   g) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 47 and a VL region comprising the        sequence set forth in SEQ ID NO: 51 [226].

In particular, the invention provides an antibody comprising at leastone antigen-binding region capable of binding to 5T4 (Trophoblastglycoprotein), wherein the antibody is able to block binding to 5T4 ofan antibody comprising a variable heavy chain (VH) region comprising thesequence set forth in SEQ ID NO: 5, and a variable light chain (VL)region comprising the sequence set forth in SEQ ID NO: 9 [059].

The antibody may in particular be able to block binding to 5T4 of anantibody selected from the group consisting of:

-   -   a) an antibody comprising a variable heavy chain (VH) region        comprising the sequence set forth in SEQ ID NO: 40 and a        variable light chain (VL) region comprising the sequence set        forth in SEQ ID NO: 44 [207],    -   b) an antibody comprising a variable heavy chain (VH) region        comprising the sequence set forth in SEQ ID NO: 47 and a        variable light chain (VL) region comprising the sequence set        forth in SEQ ID NO: 51 [226]; and an antibody comprising a        variable heavy chain (VH) region comprising the sequence set        forth in SEQ ID NO: 5 and a variable light chain (VL) region        comprising the sequence set forth in SEQ ID NO: 9 [059].

In particular embodiments of the invention, the antibody is able toblock binding to 5T4 of an antibody selected from the group consistingof:

-   -   a) an antibody comprising a variable heavy chain (VH) region        comprising the sequence set forth in SEQ ID NO: 40 and a        variable light chain (VL) region comprising the sequence set        forth in SEQ ID NO: 44 [207]; and    -   b) an antibody comprising a variable heavy chain (VH) region        comprising the sequence set forth in SEQ ID NO: 47 and a        variable light chain (VL) region comprising the sequence set        forth in SEQ ID NO: 51 [226]

The antibodies according to the invention are characterized by havingspecificity for or having the ability to bind human (Homo sapiens) 5T4.Hence, 5T4 as referred to herein may in particular be human 5T4, such asthe mature polypeptide of SEQ ID NO: 1.

In further embodiments, the antibodies of the invention arecharacterized by having specificity for or having the ability to bind tocynomolgus monkey (Macaca fascicularis) 5T4, such as specificity for orthe ability to bind to both human and cynomolgus monkey 5T4. Cynomolgusmonkey 5T4 may in particular be the mature polypeptide of SEQ ID NO: 2.

In still further embodiments, the antibodies according to the inventionhave specificity for or have the ability to bind to chicken (Gallusgallus) 5T4, such as specificity for or the ability to bind to human 5T4and chicken 5T4 or such as specificity for or the ability to bind tohuman, cynomolgus monkey and chicken 5T4, wherein chicken 5T4 inparticular may have the amino acid sequence of the mature polypeptide ofSEQ ID NO: 3.

Accordingly, the antibodies of the invention may have specificity for orbe able to bind to human 5T4 such as the mature polypeptide of SEQ IDNO: 1 and cynomologus monkey 5T4, such as the mature polypeptide of SEQID NO: 2.

Further, the antibodies according to the invention may have specificityfor or be able to bind to human 5T4, such as the mature polypeptide ofSEQ ID NO: 1, cynomologus monkey 5T4 such as the mature polypeptide ofSEQ ID NO: 2 and chicken 5T4, such as the mature polypeptide of SEQ IDNO: 3.

The antibodies according to the invention may be able to bind human 5T4,cynomolgus monkey and/or chicken 5T4, with a binding affinity thatcorresponds to a K_(D) value of 1E-7 M or less, such as a K_(D) value ofabout 1E-7 M or less, 5E-8 M or less, about 5E-8 M or less, 1E-8 M orless, about 1E-8 M or less, 5E-9 M or less, about 5E-9 M or less, suchas 1E-9 M or less or such as about 1E-9 M or less, such as with abinding affinity corresponding to a K_(D) value which is within therange of 1E-7 to 5E-10 M, such as within the range of about 1E-7 toabout 5E-10 M, such as 1E-7 to 1E-9 M, such as about 1E-7 to about 1E-9M, such as 5E-8 to 5E-10 M, such as about 5E-8 to about 5E-10 M, such as5E-8 to 1E-9 M, such as about 5E-8 to about 1E-9 M, such as 1E-8 to5E-10 M, such as about 1E-8 to about 5E-10 M, such as 1E-8 to 1E-9 M,such as about 1E-8 to about 1E-9 M, such as 1E-8 to 5E-9 M or such asabout 1E-8 to about 5E-9 M.

While it is within the capacity of the skilled person to determine theaffinity of an antibody for binding to its target, the binding affinityof the antibodies according to the invention for 5T4 may in particularbe determined by biolayer interferometry, optionally as set forth inExample 2 herein.

More specifically, the binding affinity of an antibody according to theinvention may determined using a procedure, such as a biolayerinterferometry procedure, comprising the steps of:

-   -   I) Immobilizing the antibody at an amount of 1 μg/mL for 600        seconds on an anti-human IgG Fc Capture biosensor;    -   II) Determining association over a time period of 200 seconds        and dissociation over a time period of 1000 seconds of 5T4ECDHis        (mature protein of SEQ ID NO: 99) or cynomolgus monkey 5T4        (mature protein of SEQ ID NO: 2, or recombinant cynomolgus        monkey 5T4 protein (Cusabio; cat. no. CSB-MP024093MOV), using        2-fold dilution series ranging from 100 nM to 1.56 nM.    -   III) Referencing the data to a buffer control (0 nM).

The binding affinity of an antibody according to the invention may inparticular be determined using an antibody as defined in any one of thepreceding claims, which is a monospecific, bivalent antibody, such as anantibody which is a full length IgG1.

In further embodiments of the invention, the antibody recognizes orbinds to an epitope or antibody binding region or binding site on 5T4,said binding site or epitope or antibody binding region being recognizedby any one of the antibodies selected from the group consisting of:

-   -   a) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 5 and a VL region comprising the        sequence set forth in SEQ ID NO: 9 [059],    -   b) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 12 and a VL region comprising the        sequence set forth in SEQ ID NO: 16 [076],    -   c) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 19 and a VL region comprising the        sequence set forth in SEQ ID NO: 23 [085],    -   d) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 26 and a VL region comprising the        sequence set forth in SEQ ID NO: 30 [106],    -   e) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 33 and a VL region comprising the        sequence set forth in SEQ ID NO: 37 [127],    -   f) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 40 and a VL region comprising the        sequence set forth in SEQ ID NO: 44 [207]; and    -   g) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 47 and a VL region comprising the        sequence set forth in SEQ ID NO: 51 [226].

In still further embodiments, the antibody according to the inventionrecognizes or binds to an antibody binding region, a binding site orepitope on 5T4, which is not an antibody binding region, a binding siteor epitope bound by, or is different from an antibody binding region, abinding site or epitope bound by, an antibody selected from the groupconsisting of:

-   -   a) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 87 and a VL region comprising the        sequence set forth in SEQ ID NO: 88 [H8],    -   b) an antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 83 and a VL region comprising the        sequence set forth in SEQ ID NO: 84 [A1]; and    -   c) An antibody comprising a VH region comprising the sequence        set forth in SEQ ID NO: 85 and a VL region comprising the        sequence set forth in SEQ ID NO: 86 [A3].

In other embodiments, the binding of the antibody according to theinvention to 5T4 is blocked by binding to 5T4 of an antibody comprisinga variable heavy chain (VH) region comprising the sequence set forth inSEQ ID NO: 85 and a variable light chain (VL) region comprising thesequence set forth in SEQ ID NO: 86 [A3]. An antibody comprising the VHand VL sequences set forth in SEQ ID NOs 85 and 86 respectively, isantibody A3, one of three murine 5T4 antibodies disclosed inWO2007106744. Rephrase: antibody A3 with a single aa substitution. Inthe CDR sequences?

In still other embodiments, the antibody according to the inventionshows displacement of an antibody bound to 5T4 or to His-taggedextracellular domain of 5T4 (e.g. 5T4ECDHis/mature protein of SEQ ID NO:99), said antibody bound to 5T4 comprising a variable heavy chain (VH)region comprising the sequence set forth in SEQ ID NO: 85 and a variablelight chain (VL) region comprising the sequence set forth in SEQ ID NO:86 [A3]. This displacement behavior indicates that the antibody of theinvention binds to an epitope, which is different from the epitope boundby antibody A3, but may be adjacent to or even overlapping with theepitope bound by A3.

“Displacement” or the ability to displace a bound antibody may bedetermined in a biolayer interferometry assay, such as in an assayperformed as described in Example 4 of the present application.

“Cross-blocking”, or the ability of an antibody as defined according tothe invention to block binding of another antibody to 5T4 may bedetermined by the use of a fluorescence-activated cell sorting (FACS)assay, such as in an assay performed as described in Example 5.

In particular, “cross-blocking”, or the ability of an antibody accordingto the invention to block binding of another antibody to 5T4, isdetermined as the ability of an unconjugated antibody to block bindingof a conjugated antibody, and is optionally determined in a procedurecomprising the steps of:

-   -   i) Providing a set of samples, each sample comprising a mixture        of human ovary adenocarcinoma SK-OV-3 cells, an antibody which        binds to 5T4 and is conjugated to fluorescein isothiocyanate        (FITC), and an excess of unconjugated antibody targeting 5T4,    -   ii) Incubating the samples for 30 minutes at 4° C., and        thereafter subjecting the samples to centrifugation,    -   iii) Removing the supernatant from each sample and resuspending        the cells in buffer and determining mean fluorescence intensity        (MFI) of FITC using a flow cytometer; and    -   iv) Calculating the percentage of binding as following:        -   The difference in MFI between cells incubated with a mixture            of FITC-conjugated antibodies and unconjugated antibodies            and cells incubated without FITC-conjugated or unconjugated            antibodies, multiplied by 100, and subsequently divided by            the difference in MFI between cells incubated with a mixture            of FITC-conjugated antibodies and IgG-b12 antibodies and            cells incubated without FITC-conjugated or unconjugated            antibodies.

While the skilled person will be familiar with suitable technologies fordetermining the ability of an antibody to block the binding of anotherantibody to its target, or to displace another antibody bound to itstarget, the present application discloses procedures suitable fordetermining blocking of binding and displacement. Hence, in someembodiments, the ability of an antibody according to the invention toblock binding of another antibody to 5T4 or to displace another antibodybound to 5T4, may be determined using biolayer interferometry, such asin biolayer interferometry performed as described in Example 3.

In particular, the ability of an antibody according to the invention toblock binding of another antibody to 5T4, or to displace anotherantibody bound to 5T4 is determined using biolayer interferometry may bedetermined in a procedure comprising the steps of:

-   -   i) Immobilizing the antibody according to the invention, at an        amount of 20 μg/mL in 10 mM sodium acetate buffer to an        activated Amine-Reactive 2^(nd) Generation biosensor,    -   ii) Quenching the biosensor with the immobilized antibody in        ethanolamine pH 8.5,    -   iii) Immersing the biosensor with the immobilized antibody in a        composition comprising 3.6 μg/mL (100 nM) of human 5T4ECDHis        (mature protein of SEQ ID NO: 99) for a time period of 500        seconds, and then    -   iv) Immersing the biosensor with the immobilized antibody and        5T4ECDHis in a composition comprising 10 μg/mL of the other        antibody targeting 5T4 and determining the association response        over a time period of 500 seconds;    -   wherein steps i)-iv) are performed at a temperature of 30° C.        and with shaking at 1000 rpm.

The antibodies provided herein may bind to an epitope or antibodybinding region on human 5T4 comprising the amino acid residues R73, Y92and R94; the numbering of each amino acid residue referring to itsposition in SEQ ID NO: 1.

Also provided herein are antibodies, which bind to an epitope orantibody binding region on human 5T4 comprising the amino acid residuesS69, R73, Y92 and R94; the numbering of each amino acid residuereferring to its position in SEQ ID NO: 1.

Further provided herein are antibodies, which bind to an epitope orantibody binding region on human 5T4 comprising the amino acid residuesR73, T74, Y92, R94 and N95; the numbering of each amino acid residuereferring to its position in SEQ ID NO: 1.

Based on the results provided in Example 16 herein it is hypothesized,without any wish to be bound by theory, that any one or more of theseamino acid residues (i.e. S69, R73, T74, Y92, R94 and N95) is/aredirectly involved in binding of the antibody, such as by way ofnon-covalent interactions; e.g with amino acid residues within the CDRsequences of the antibody. The hypothesis is supported by the fact thatthese residues were identified as being surface-exposed on the structureof 5T4 (4 cnm; provided in the RCSB PDB Protein Data Bank; DOI:10.2210/pdb4CNM/pdb) as published in Zhao, Y., Malinauskas, T., Harlos,K., & Jones, E. Y. (2014). Structural insights into the inhibition ofWnt signaling by cancer antigen 5T4/Wnt-activated inhibitory factor 1.Structure, 22(4), 612-620.

One or more of the following additional amino acid residues may beinvolved binding of the antibody, such as indirectly involved inbinding, e.g. by impacting protein folding and/or positioning of one ormore amino acid residues directly involved in binding of the antibody:L89, F111, L117, F138, L144, D148, N152; the numbering of each aminoacid residue referring to its position in SEQ ID NO: 1. In particular,L89, F111, L117, F138, L144 have been identified as part of ahydrophobic core within 5T4 as described by Zhao et al., Structure,22(4), 612-620.

Further, the antibody disclosed herein may to an epitope or antibodybinding region on human 5T4 within which amino acid residues R73, Y92and R94 are directly involved in binding the antibody, and wherein oneor more of amino acid residues F111, F138, L144 and D148 are indirectlyinvolved in said binding; the numbering of each amino acid residuereferring to its position in SEQ ID NO: 1.

The antibody provided herein may bind to an epitope or antibody bindingregion on human 5T4 within which amino acid residues S69, R73, Y92 andR94 are directly involved in binding the antibody, and wherein one ormore of amino acid residues F111, F138, and D148 are indirectly involvedin said binding; the numbering of each amino acid residue referring toits position in SEQ ID NO: 1.

Also, the present disclosure provides antibodies which bind to anepitope or antibody binding region on human 5T4 within which amino acidresidues R73, T74, Y92, R94 and N95 are directly involved in binding theantibody, and wherein amino acid residue F138 is indirectly involved insaid binding; the numbering of each amino acid residue referring to itsposition in SEQ ID NO: 1.

The amino acid residues comprised by said epitope or antibody bindingregion and optionally the one or more additional amino acid residueswhich are indirectly involved in binding may be identified by alaninescanning of human 5T4 having the amino acid sequence set forth in SEQ IDNO: 1 or the mature polypeptide sequence of SEQ ID NO: 1, or by alaninescanning of of a polypeptide comprising amino acid residues 32-355 ofSEQ ID NO: 1.

The alanine scanning may in particular be performed as set forth oressentially as set forth in Example 16 herein.

Further, the alanine scanning may be performed by a procedure comprisingthe steps of:

-   -   i) Expressing mutant human 5T4 polypeptides in which all amino        acid residues in the extracellular domain of human 5T4        (corresponding to amino acid residues 32-355 of SEQ ID NO: 1),        except cysteines and alanines, are individually substituted with        alanine, and wild type 5T4 polypeptides (amino acid residues        32-355 of SEQ ID NO: 1) individually in human embryonic kidney        cells, e.g. HEK 293 cells, such that for each mutant or wild        type 5T4 a sample comprising 70-90.000 cells, such as 80.000        cells is provided,    -   ii) Incubating the cells in each sample with 20 μL of said        antibody conjugated to fluorescein isothiocyanate        (FITC)-conjugated antibody (3 μg/mL; in FACS buffer) for 40        minutes at room temperature, and subsequently washing each        sample twice in 150-180 μL FACS buffer (phosphate-buffered        saline [PBS; Lonza, cat. no. BE17-517]+0.1% [w/v] BSA [Roche,        cat. no. 10735086001]+0.02% [w/v] sodium azide [NaN₃; EMELCA        Bioscience, cat. no. 41920044-3]) and resuspending the cells in        each sample in 30 μL FACS buffer,    -   iii) Determining, for each sample, the average amount of        antibody bound per cell as the geometric mean of the        fluorescence intensity (gMFI) for the viable, single cell        population in said sample and normalizing the data for each test        antibody against the binding intensity of a non-cross blocking        5T4-specific control antibody using the equation:

${{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} = {{Log}_{10}\left( \frac{{gMFI}_{{Test}\mspace{11mu}{Ab}}}{{gMFI}_{{Control}\mspace{11mu}{Ab}}} \right)}$

-   -   -   wherein ‘aa position’ refers to the position that was            mutated into an alanine,        -   wherein the Z-score is calculated to express loss or gain of            binding of the antibody, according to the calculation:

${Z - {{score}\left( {{fold}\mspace{14mu}{change}} \right)}} = \frac{{{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} - \mu}{\sigma}$

-   -   -   wherein μ and σ are the mean and standard deviation,            respectively, of the Normalized gMFI calculated from all            mutants,        -   wherein data is excluded from the analysis if the gMFI of            the control antibody for a particular 5T4 mutant is lower            than the mean gMFI_(Control Ab)-2.5×SD of the mean            gMFI_(Control Ab) (from all mutants); and optionally        -   wherein data is excluded from the analysis if a residue            binds with a Z-score just below −1.5 (e.g. between −1.5 and            −1.8, such as between −1.5 and −1.7 or such as between −1.5            and −1.6) and that residue is predicted to be buried and            spatially separated from the majority of residues, which are            predicted to be surface-exposed and for which loss of            binding or reduced binding is determined.

A suitable non-cross blocking 5T4-specific control antibody to be usedin step iii) is a bispecific antibody comprising

-   -   an antigen-binding region, which comprises a VH sequence as set        forth in SEQ ID NO: 83 and a VL sequence as set forth in SEQ ID        NO: 84 [A1]; and    -   an antigen binding region, which comprises a VH sequence as set        forth in SEQ ID NO: 97 and a VL sequence as set forth in SEQ ID        NO: 98 [B12].

The present invention provides antibodies which bind to 5T4 such thatthere is loss of binding or binding is reduced if any one or more of theamino acid residues R73, Y92 and R94 is/are substituted with alanine;the numbering of each amino acid residue referring to its position inSEQ ID NO: 1.

In particular, the antibodies may bind to 5T4 such that there is loss ofbinding or binding is reduced if any one or more of the amino acidresidues S69, R73, Y92 and R94 is/are substituted with alanine; thenumbering of each amino acid residue referring to its position in SEQ IDNO: 1.

Further, the antibodies may bind to 5T4 such that there is loss ofbinding or binding is reduced if any one or more of the amino acidresidues R73, T74, Y92, R94 and N95 is/are substituted with alanine; thenumbering of each amino acid residue referring to its position in SEQ IDNO: 1.

Also, the antibodies disclosed herein may bind to 5T4 such that there isloss of binding or binding is reduced if any one or more of the aminoacid residues: L89, F111, L117, F138, L144, D148, N152 is/aresubstituted with alanine; the numbering of each amino acid residuereferring to its position in SEQ ID NO: 1.

Further, the antibodies may bind to 5T4 such that there is loss ofbinding or binding is reduced if any one or more of the amino acidresidues R73, Y92, R94, F111, F138, L144 and D148 is/are substitutedwith alanine; the numbering of each amino acid residue referring to itsposition in SEQ ID NO: 1.

The antibodies may bind to 5T4 such that there is loss of binding orbinding is reduced if any one or more of the amino acid residues S69,R73, Y92, R94, F111, F138, and D148 is/are substituted with alanine; thenumbering of each amino acid residue referring to its position in SEQ IDNO: 1.

In other embodiments, the antibodies of the invention may bind to 5T4such that there is loss of binding or binding is reduced if any one ormore of the amino acid residues R73, T74, Y92, R94, N95 and F138 is/aresubstituted with alanine; the numbering of each amino acid residuereferring to its position in SEQ ID NO: 1.

The the effect of any of the alanine substitutions provided above may bedetermined by alanine scanning of a polypeptide comprising amino acidresidues 32-355 of SEQ ID NO: 1.

In particular, the effect of the alanine substitutions may be determinedby a procedure as set forth or essentially as set forth in Example 16herein.

Loss of binding may be defined as a Z-score in binding being lower than1.5; the Z-score optionally being calculated as set forth or essentiallyas set forth in Example 16 herein.

The effect of any of the alanine substitutions may be determined by aprocedure comprising the steps of:

-   -   i) Expressing mutant human 5T4 polypeptides in which all amino        acid residues in the extracellular domain of human 5T4        (corresponding to amino acid residues 32-355 of SEQ ID NO: 1),        except cysteines and alanines, are individually substituted with        alanine, and wild type 5T4 polypeptides individually in human        embryonic kidney cells, e.g. HEK 293 cells, such that for each        mutant or wild type 5T4 a sample comprising 70-90.000 cells,        such as 80.000 cells is provided,    -   ii) Incubating the cells in each sample with 20 μL of said        antibody conjugated to fluorescein isothiocyanate        (FITC)-conjugated antibody (3 μg/mL; in FACS buffer) for 40        minutes at room temperature, and subsequently washing each        sample twice in 150-180 μL FACS buffer (phosphate-buffered        saline [PBS; Lonza, cat. no. BE17-517]+0.1% [w/v] BSA [Roche,        cat. no. 10735086001]+0.02% [w/v] sodium azide [NaN₃; EMELCA        Bioscience, cat. no. 41920044-3]) and resuspending the cells in        each sample in 30 μL FACS buffer,    -   iii) Determining, for each sample, the average amount of        antibody bound per cell as the geometric mean of the        fluorescence intensity (gMFI) for the viable, single cell        population in said sample and normalizing the data for each test        antibody against the binding intensity of a non-cross blocking        5T4-specific control antibody using the equation:

${{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} = {{Log}_{10}\left( \frac{{gMFI}_{{Test}\mspace{11mu}{Ab}}}{{gMFI}_{{Control}\mspace{11mu}{Ab}}} \right)}$

-   -   -   wherein ‘aa position’ refers to the position that was            mutated into an alanine,        -   wherein the Z-score is calculated to express loss or gain of            binding of the antibody, according to the calculation:

${Z - {{score}\left( {{fold}\mspace{14mu}{change}} \right)}} = \frac{{{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} - \mu}{\sigma}$

-   -   -   wherein μ and σ are the mean and standard deviation,            respectively, of the Normalized gMFI calculated from all            mutants,        -   wherein data is excluded from the analysis if the gMFI of            the control antibody for a particular 5T4 mutant is lower            than the mean gMFI_(Control Ab)-2.5×SD of the mean            gMFI_(Control Ab) (from all mutants); and optionally        -   wherein data is excluded from the analysis if a residue            binds with a Z-score just below −1.5 (e.g. between −1.5 and            −1.8, such as between −1.5 and −1.7 or such as between −1.5            and −1.6) and that residue is predicted to be buried and            spatially separated from the majority of residues, which are            predicted to be surface-exposed and for which loss of            binding or reduced binding is determined.

A suitable non-cross blocking 5T4-specific control antibody in step iii)of the procedure above is a bispecific antibody comprising

-   -   an antigen-binding region, which comprises a VH sequence as set        forth in SEQ ID NO: 83 and a VL sequence as set forth in SEQ ID        NO: 84 [A1]; and    -   an antigen binding region, which comprising a VH sequence as set        forth in SEQ ID NO: 97 and a VL sequence as set forth in SEQ ID        NO: 98 [B12].

The antibody according to the invention may be characterized by havingreduced internalization capacity as shown by reduced cytotoxicity whenconjugated to a cytotoxic moiety as compared to a likewise conjugatedantibody comprising a variable heavy chain (VH) region comprising thesequence set forth in SEQ ID NO: 87 and a variable light chain (VL)region comprising the sequence set forth in SEQ ID NO: 88 [H8]. Anantibody comprising the VH and VL sequences set forth in SEQ ID Nos: 87and 88 respectively, may be murine 5T4 antibody mAb5T4, also called theH8 antibody, (Shaw et al. (2002), Biochem. J. 363: 137-45, WO98/55607).Various chimeric or humanized versions of antibody H8 are disclosed inWO06/031653.

Cytotoxicity or internalization of 5T4 antibodies that monovalently bind5T4 may be determined using a procedure as set forth in Example 7 in thepresent application. In particular, cytotoxicity may be determined in anassay comprising the steps of:

-   -   i) Providing an toxin-conjugated bispecific antibody that        monovalently binds 5T4, comprising a first-Fab arm of an        antibody as defined in any one of the preceding claims and a        second Fab arm capable of binding to HIV viral protein gp120        (HIV-1 gp120), wherein the HIV-1 gp120-specific Fab-arm is        conjugated to Duostatin-3,    -   ii) Incubating 5T4-positivie breast cancer cells MDA-MB-468        (ATCC clone HTB-132) or HCC1954 (ATCC clone CRL-1338) with said        bispecific antibody that monovalently binds 5T4 for 5 days at        37° C.; and    -   iii) Determining the viability of the cells.

IgG-b12 is a HIV-1 gp120 specific antibody (Barbas, C F. J Mol Biol.1993 Apr. 5; 230(3):812-23). Sequences of the heavy chain (VH) and lightchain variable regions (VL) are set forth in SEQ ID NOs: 97 and 98,respectively.

In certain embodiments, the antibody of the invention is one, whereinsaid antigen-binding region, which is capable of binding to 5T4comprises a heavy chain variable region (VH) selected from the groupconsisting of:

-   -   a) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 6, 7 and 8 [059],    -   b) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 13, 14 and 15 [076],    -   c) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 20, 21 and 22 [085],    -   d) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 27, 28 and 29 [106],    -   e) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 34, 35 and 36 [127],    -   f) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 41, 42 and 43 [207],    -   g) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 48, 49 and 50 [226]; and    -   h) a heavy chain variable region (VH) comprising CDR1, CDR2 and        CDR3 sequences, said CDR1, CDR2 and CDR3 sequences comprising in        total, at the most 1, 2, 3, 4, 5, 6, 7, 8, 9 or at the most 10        amino acid substitutions, when compared to the CDR1, CDR2 and        CDR3 sequences defined in any one of a) to g).

In other embodiments, the antibody according to the invention is one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) selected from the group consistingof:

-   -   a) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 6, 7 and 8 [059],    -   b) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 41, 42 and 43 [207];    -   c) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 48, 49 and 50 [226]; and    -   d) a heavy chain variable region (VH) comprising CDR1, CDR2 and        CDR3 sequences, said CDR1, CDR2 and CDR3 sequences comprising in        total, at the most 1, 2, 3, 4, 5, 6, 7, 8, 9 or at the most 10        amino acid substitutions, when compared to the CDR1, CDR2 and        CDR3 sequences defined in any one of a) to c).

In particular, the antibody according to the invention may be one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3sequences of SEQ ID NOs.: 6, 7 and 8 [059].

Alternatively, the antibody according to the invention may be one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) selected from the group consistingof: a heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3sequences of SEQ ID NOs.: 41, 42 and 43 [207].

Also, the antibody according to the invention may be one, wherein saidantigen-binding region capable of binding to 5T4 comprises a heavy chainvariable region (VH) selected from the group consisting of: a heavychain variable region (VH) comprising CDR1, CDR2, and CDR3 sequences ofSEQ ID NOs.: 48, 49 and 50 [226].

In other embodiments, the antibody according to the invention is one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) and a light chain variable region(VL) selected from the group consisting of:

-   -   a) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 6, 7 and 8, respectively, and        a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NO: 10, AAS and SEQ ID NO: 11,        respectively [059],    -   b) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 13, 14 and 15, respectively;        and a light chain variable region (VL) comprising the CDR1,        CDR2, and CDR3 sequences of SEQ ID NO: 17, DAS and SEQ ID NO:18,        respectively [076],    -   c) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 20, 21 and 22, respectively;        and a light chain variable region (VL) comprising the CDR1,        CDR2, and CDR3 sequences of SEQ ID NO: 24, DAS and SEQ ID NO:        25, respectively [085],    -   d) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 27, 28 and 29, respectively;        and a light chain variable region (VL) comprising the CDR1,        CDR2, and CDR3 sequences of SEQ ID NO: 31, DVS and SEQ ID NO:        32, respectively [106],    -   e) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 34, 35 and 36, respectively;        and a light chain variable region (VL) comprising the CDR1,        CDR2, and CDR3 sequences of SEQ ID NO: 38, DAS and SEQ ID NO:        39, respectively [127],    -   f) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 41, 42 and 43, respectively,        and a light chain variable region (VL) comprising the CDR1,        CDR2, and CDR3 sequences of SEQ ID NO: 45, DAS and SEQ ID NO:        46, respectively [207],    -   g) a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 48, 49 and 50, respectively,        and a light chain variable region (VL) region comprising the        CDR1, CDR2, and CDR3 sequences of SEQ ID NO: 52, DAS and SEQ ID        NO: 53, respectively [226]; and    -   h) a heavy chain variable region (VH) comprising CDR1, CDR2 and        CDR3 sequences, said CDR1, CDR2 and CDR3 sequences comprising in        total, at the most 1, 2, 3, 4, 5, 6, 7, 8, 9 or at the most 10        amino acid substitutions, when compared to the CDR1, CDR2 and        CDR3 sequences defined in any one of a) to g).

The antibody according to the invention may be an antibody, wherein thesix complementarity-determining regions (CDRs) of the antigen bindingregion(s) capable of binding to 5T4 comprise, in total, at the most 1,2, 3, 4, 5, 6, 7, 8, 9 or at the most 10 amino acid substitutions, whencompared to

-   -   i) the CDR sequences of SEQ ID NOs: 6, 7, 8, 10, AAS and SEQ ID        NO: 11 [059],    -   ii) the CDR sequences of SEQ ID NOs.: 41, 42, 43, 45, DAS and        SEQ ID NO: 46 [207]; or    -   iii) the CDR sequences of SEQ ID NOs.: 48, 49, 50, 52, DAS and        SEQ ID NO: 53 [226].

Preferably 1, such as 2, 3, 4, 5, 6, 7, 8, 9 or 10 of the said aminoacid substitutions is/are conservative amino acid substitution(s).

The antibody may in particular comprise one or two heavy chain variableregions in which the complementarity-determining region 3 (CDR3)comprises six consecutive amino acid residues of the sequence set forthin SEQ ID NO: 102 (YYGMDV) [059, 207, 226]. These six consecutive aminoacid residues may be the most C-terminal amino acid residues within theCDR3.

The antibody according to the invention may be an antibody, wherein saidantigen-binding region capable of binding to 5T4 comprises one or twoheavy chain variable region(s) (VH) comprising the CDR1 sequence of SEQID NO: 41 (GGSFSGYY), the CDR2 sequence of SEQ ID NO: 103 (IDHSX₁ST),and the CDR3 sequence of SEQ ID NO: 104 (AX₂WFGELX₃X₄YYYGMDV), and alight chain variable region (VL) comprising the CDR1 sequence of SEQ IDNO: 105 (QSVSSX₅), the CDR2 sequence DAS, and the CDR3 sequence of SEQID NO: 46 (QQRSNWPLT), and wherein X₁ is G or E, X₂ is A or G, X₃ is Wor Y, X₄ is D or H and X₅ is Y or F [207, 226].

The antibody according to the invention may be one, wherein saidantigen-binding region capable of binding to 5T4 comprises a heavy chainvariable region (VH) comprising the CDR1, CDR2, and CDR3 sequences ofSEQ ID NOs.: 6, 7, and 8, respectively, and a light chain variableregion (VL) comprising the CDR1, CDR2, and CDR3 sequences of SEQ ID NO:10, AAS and SEQ ID NO: 11, respectively [059].

Alternatively, the antibody according to the invention may be one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) comprising the CDR1, CDR2, and CDR3sequences of SEQ ID NOs.: 41, 42 and 43, respectively, and a light chainvariable region (VL) comprising the CDR1, CDR2, and CDR3 sequences ofSEQ ID NO: 45, DAS and SEQ ID NO: 46, respectively [207].

Additionally, the antibody according to the invention may be one,wherein said antigen-binding region capable of binding to 5T4 comprisesa heavy chain variable region (VH) comprising the CDR1, CDR2, and CDR3sequences of SEQ ID NOs.: 48, 49 and 50, respectively, and a light chainvariable region (VL) comprising the CDR1, CDR2, and CDR3 sequences ofSEQ ID NO: 52, DAS and 53, respectively [226].

In some embodiments, the antibody according to the invention is anantibody, wherein said antigen-binding region capable of binding to 5T4comprises a heavy chain variable region (VH) selected from the groupconsisting of:

-   -   a) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 5 or a sequence having at least 90%, at least 95%, at        least 97%, or at least 99% amino acid sequence identity to the        sequence of SEQ ID NO: 5 [059],    -   b) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 12 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 12 [076],    -   c) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 19 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 19 [085],    -   d) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 26 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 26 [106],    -   e) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 33 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 33 [127],    -   f) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 40 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 40 [207]; and    -   g) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 47 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 47 [226].

The antibody according to the invention may in particular be anantibody, wherein said antigen-binding region capable of binding to 5T4comprises a heavy chain variable region (VH) comprising the sequence ofSEQ ID NO: 5 or a sequence having at least 90%, at least 95%, at least97%, or at least 99% amino acid sequence identity to the sequence of SEQID NO: 5 [059].

Also, the antibody according to the invention may be one, wherein saidantigen-binding region capable of binding to 5T4 comprises a heavy chainvariable region (VH) comprising the sequence of SEQ ID NO: 40 or asequence having at least 90%, at least 95%, at least 97%, or at least99% amino acid sequence identity to the sequence of SEQ ID NO: 40 [207].

Additionally, the antibody according to the invention may be anantibody, wherein said antigen-binding region capable of binding to 5T4comprises a heavy chain variable region (VH) comprising the sequence ofSEQ ID NO: 47 or a sequence having at least 90%, at least 95%, at least97%, or at least 99% amino acid sequence identity to the sequence of SEQID NO: 47 [226].

In other embodiments, the antibody according to the invention is anantibody, wherein said antigen-binding region capable of binding to 5T4comprises a heavy chain variable region (VH) and a light chain variableregion (VL) selected from the group consisting of:

-   -   a) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 5 or a sequence having at least 90%, at least 95%, at        least 97%, or at least 99% amino acid sequence identity to the        sequence of SEQ ID NO: 5, and a light chain variable region (VL)        comprising the sequence of SEQ ID NO: 9 or a sequence having at        least 90%, at least 95%, at least 97%, or at least 99% amino        acid sequence identity to the sequence of SEQ ID NO: 9 [059],    -   b) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 12 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 12, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 16 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 16        [076],    -   c) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 19 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 19, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 23 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 23        [085],    -   d) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 26 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 26, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 30 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 30        [106],    -   e) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 33 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 33, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 37 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 37        [127],    -   f) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 40 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 40, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 44 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 44        [207],    -   g) a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 47 or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 47, and a light chain variable region        (VL) comprising the sequence of SEQ ID NO: 51 or a sequence        having at least 90%, at least 95%, at least 97%, or at least 99%        amino acid sequence identity to the sequence of SEQ ID NO: 51        [226].

In one embodiment, the at least one binding region comprises a variableheavy chain (VH) region and a variable light chain (VL) region having atmost 10 mutations or substitutions, at most 5 mutations orsubstitutions, such as at most 4 mutations or substitutions, such as atmost 3 mutations or substitutions, such as at most 2 mutations orsubstitutions, such as at most 1 mutation or substitution, across saidheavy chain variable region (VH) and light chain variable region (VL)region selected from the group consisting of:

-   -   a) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 5, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 9 [059],    -   b) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 12, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 16 [076],    -   c) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 19, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 23 [085],    -   d) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 26, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 30 [106],    -   e) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 33, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 37 [127],    -   f) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 40, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 44 [207],    -   g) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 47, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 51 [226].

In some embodiments of the present disclosure, the at most 10 mutationsor substitutions, at most 5 mutations or substitutions, such as at most4 mutations or substitutions, such as at most 3 mutations orsubstitutions, such as at most 2 mutations or substitutions, such as atmost 1 mutation or substitution are allowed across the full length ofthe variable heavy chain and the entire variable light chain. In otherembodiments, the at most 10 mutations or substitutions, at most 5mutations or substitutions, such as at most 4 mutations orsubstitutions, such as at most 3 mutations or substitutions, such as atmost 2 mutations or substitutions, such as at most 1 mutation orsubstitution may not be within any of the 6 CDR sequences in the saidvariable heavy chain and the variable light chain.

The up to 10 mutations or substitutions may be distributed across thefull length of the variable heavy chain and the variable light chain ofeach binding region. Some or all of the mutations or substitutions maybe conservative substitutions in which one amino acid residue issubstituted with an amino acid residue of the same class as indicatedunder the definition “amino acid” herein above; for instance an acidicamino acid being substituted for another acidic amino acid residue, andan aromatic residue may be substituted for another aromatic residue. Itmay be preferred that 35% or more, 50% or more, 60% or more, 70% ormore, 75% or more, 80% or more, 85% or more, 90% or more, 92% or more,93% or more or 94% or more of the substitutions in the variant areconservative amino acid residue replacements.

In particular, some or all of the mutations or substitutions may be withamino acid residue(s) each having the same physical or functionalproperties as the respective amino acid residue which they substitute.Amino acid residues sharing physical and functional properties areprovided under the definition “amino acid” herein above; for instance aunder the definition “amino acid” herein above; for instance ahydrophobic residue may be substituted for another hydrophobic aminoacid residue or a cycloalkenyl-associated residue may be substituted foranother cycloalkenyl-associated residue.

Antibodies comprising substitutions or mutations as disclosed above mayin particular be functional variants of the VL regions, VH regions, orone or more CDRs defined above with reference to sequences identifiers.A functional variant of a VL, VH, or CDR used in the context of theantibodies of the present invention still allows the antibody to retainat least a substantial proportion (at least about 50%, 60%, 70%, 80%,90%, 95%, 99% or more) of the affinity and/or thespecificity/selectivity of the parent antibody, and in some cases suchan 5T4 antibody may even be associated with greater affinity,selectivity and/or specificity than the parent antibody.

In further embodiments of the invention, the antibody is one, whereinsaid antigen-binding region capable of binding to 5T4 comprises a heavychain variable region (VH) and a light chain variable region (VL)selected from the group consisting of:

-   -   a) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 5, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 9 [059],    -   b) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 12, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 16 [076],    -   c) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 19, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 23 [085],    -   d) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO:

26, and a light chain variable region (VL) comprising or consisting ofthe sequence of SEQ ID NO: 30 [106],

-   -   e) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 33, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 37 [127],    -   f) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 40, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 44 [207]; and    -   g) a heavy chain variable region (VH) comprising or consisting        of the sequence of SEQ ID NO: 47, and a light chain variable        region (VL) comprising or consisting of the sequence of SEQ ID        NO: 51 [226].

The antibody of the invention may be a full-length antibody, such as afull length IgG1 antibody.

Further, the antibody of the invention may be a monovalent antibody.Alternatively, the antibody according to the invention may be a bivalentantibody.

In other embodiments, the antibody provided according to the presentinvention is a monospecific antibody.

Alternatively, the antibody according to the present disclosure may be abispecific antibody.

It is further within the scope of the present disclosure to provide anantibody as defined above, the antibody comprising an antigen bindingregion of an antibody that binds to CD3, such as human CD3E (epsilon),such as human CD3E (epsilon) as specified in SEQ ID NO: 4.

In particular, the present disclosure provides a bispecific antibodycomprising a first antigen binding region of an antibody as disclosedabove, and a second binding region which binds to CD3, such as human CD3as defined above.

Examples of bispecific antibody molecules which may be used in thepresent invention include but are not limited to (i) a single antibodythat has two arms comprising different antigen-binding regions, (ii) asingle chain antibody that has specificity to two different epitopes,e.g., via two scFvs linked in tandem by an extra peptide linker; (iii) adual-variable-domain antibody (DVD-Ig™), where each light chain andheavy chain contains two variable domains in tandem through a shortpeptide linkage Wu et al., Generation and Characterization of a DualVariable Domain Immunoglobulin (DVD-Ig™) Molecule, In: AntibodyEngineering, Springer Berlin Heidelberg (2010); (iv) a chemically-linkedbispecific (Fab′)2 fragment; (v) a Tandab®, which is a fusion of twosingle chain diabodies resulting in a tetravalent bispecific antibodythat has two binding sites for each of the target antigens; (vi) aflexibody, which is a combination of scFvs with a diabody resulting in amultivalent molecule; (vii) a so called “dock and lock” molecule(Dock-and-Lock®, based on the “dimerization and docking domain” inProtein Kinase A, which, when applied to Fabs, can yield a trivalentbispecific binding protein consisting of two identical Fab fragmentslinked to a different Fab fragment; (viii) a so-called Scorpionmolecule, comprising, e.g., two scFvs fused to both termini of a humanFab-arm; and (ix) a diabody.

In one embodiment, the bispecific antibody of the present invention is adiabody, a cross-body, such as CrossMabs, or a bispecific antibodyobtained via a controlled Fab arm exchange (such as described in WO2011/131746).

Examples of different classes of bispecific antibodies include but arenot limited to (i) IgG-like molecules with complementary CH3 domains toforce heterodimerization; (ii) recombinant IgG-like dual targetingmolecules, wherein the two sides of the molecule each contain the Fabfragment or part of the Fab fragment of at least two differentantibodies; (iii) IgG fusion molecules, wherein full length IgGantibodies are fused to extra Fab fragment or parts of Fab fragment;(iv) Fc fusion molecules, wherein single chain Fv molecules orstabilized diabodies are fused to heavy-chain constant-domains,Fc-regions or parts thereof; (v) Fab fusion molecules, wherein differentFab-fragments are fused together, fused to heavy-chain constant-domains,Fc-regions or parts thereof; and (vi) ScFv- and diabody-based and heavychain antibodies (e.g., domain antibodies, Nanobodies®) whereindifferent single chain Fv molecules or different diabodies or differentheavy-chain antibodies (e.g. domain antibodies, Nanobodies®) are fusedto each other or to another protein or carrier molecule fused toheavy-chain constant-domains, Fc-regions or parts thereof.

Examples of IgG-like molecules with complementary CH3 domains moleculesinclude but are not limited to the Triomab® (Trion Pharma/FreseniusBiotech, WO/2002/020039), the Knobs-into-Holes (Genentech, WO9850431),CrossMAbs (Roche, WO2011117329) and the electrostatically-matched(Amgen, EP1870459 and WO2009089004; Chugai, US201000155133; Oncomed,WO2010129304), the LUZ-Y (Genentech), DIG-body and PIG-body(Pharmabcine), the Strand Exchange Engineered Domain body (SEEDbody)(EMDSerono, WO2007110205), the Biclonics (Merus), FcΔAdp (Regeneron, WO2010/015792), bispecific IgG1 and IgG2 (Pfizer/Rinat, WO11143545),Azymetric scaffold (Zymeworks/Merck, WO2012058768), mAb-Fv (Xencor,WO2011028952), bivalent bispecific antibodies (Roche WO 2009/080254) andDuoBody® molecules (Genmab A/S, WO 2011/131746).

Examples of recombinant IgG-like dual targeting molecules include butare not limited to Dual Targeting (DT)-Ig (GSK/Domantis), Two-in-oneAntibody (Genentech), Cross-linked Mabs (Karmanos Cancer Center), mAb2(F-Star, WO2008003116), Zybodies™ (Zyngenia), approaches with commonlight chain (Crucell/Merus, U.S. Pat. No. 7,262,028), κλBodies(NovImmune) and CovX-body (CovX/Pfizer).

Examples of IgG fusion molecules include but are not limited to DualVariable Domain (DVD)-Ig™ (Abbott, U.S. Pat. No. 7,612,181), Dual domaindouble head antibodies (Unilever; Sanofi Aventis, WO20100226923),IgG-like Bispecific (ImClone/Eli Lilly), Ts2Ab (MedImmune/AZ) and BsAb(Zymogenetics), HERCULES (Biogen Idec, US007951918), scFv fusion(Novartis), scFv fusion (Changzhou Adam Biotech Inc, CN 102250246) andTvAb (Roche, WO2012025525, WO2012025530).

Examples of Fc fusion molecules include but are not limited to ScFv/FcFusions (Academic Institution), SCORPION (Emergent BioSolutions/Trubion,Zymogenetics/BMS), Dual Affinity Retargeting Technology (Fc-DART′)(MacroGenics, WO2008157379, WO2010/080538) and Dual(ScFv)2-Fab (NationalResearch Center for Antibody Medicine—China).

Examples of Fab fusion bispecific antibodies include but are not limitedto F(ab)2 (Medarex/AMGEN), Dual-Action or Bis-Fab (Genentech),Dock-and-Lock® (DNL) (ImmunoMedics), Bivalent Bispecific (Biotecnol) andFab-Fv (UCB-Celltech).

Examples of scFv-, diabody-based and domain antibodies include but arenot limited to Bispecific T Cell Engager (BiTE®) (Micromet, TandemDiabody (Tandab™) (Affimed), Dual Affinity Retargeting Technology (DART)(MacroGenics), Single-chain Diabody (Academic), TCR-like Antibodies(AIT, ReceptorLogics), Human Serum Albumin ScFv Fusion (Merrimack) andCOMBODY (Epigen Biotech), dual targeting Nanobodies® (Ablynx), dualtargeting heavy chain only domain antibodies.

The antibody according to the present disclosure may in particular be anantibody, wherein the antigen binding region that binds to CD3 comprises

-   -   a heavy chain variable region (VH) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ    -   ID NOs.: 54, 55 and 56, respectively; [huCD3-H1L1] (WO2015001085        (Genmab A/S)); and, optionally    -   a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NO: 58, GTN and 59, respectively        [huCD3-H1L1].

Also disclosed are antibodies wherein the antigen binding region thatbinds to CD3 comprises

-   -   a heavy chain variable region (VH) comprising the sequence of        SEQ ID NO: 57, or a sequence having at least 90%, at least 95%,        at least 97%, or at least 99% amino acid sequence identity to        the sequence of SEQ ID NO: 57 [huCD3-H1L1];    -   and, optionally        -   a light chain variable region (VL) comprising the sequence            of SEQ ID NO: 60 or a sequence having at least 90%, at least            95%, at least 97%, or at least 99% amino acid sequence            identity to the sequence of SEQ ID NO: 60, [huCD3-H1L1].

The present disclosure further provides an antibody, wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        sequences of SEQ ID NOs.: 6, 7 and 8, respectively, and a light        chain variable region (VL) comprising the CDR1, CDR2, and CDR3        sequences of SEQ ID NO: 10, AAS and 11, respectively [059];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55 and 56,        respectively, and a light chain variable region (VL) comprising        CDR1, CDR2, and CDR3 having the sequences as set forth in SEQ ID        NO: 58, the sequence GTN, and the sequence as set forth in SEQ        ID NO: 59 [huCD3-H1L1], respectively.

Also, the disclosure provides an antibody, wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the CDR1, CDR2, and        CDR3 sequences of SEQ ID NOs.: 41, 42 and 43, respectively, and        a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NOs.: 45, DAS and 46, respectively        [207];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55 and 56,        respectively, and a light chain variable region (VL) comprising        CDR1, CDR2, and CDR3 having the sequences as set forth in SEQ ID        NO: 58, the sequence GTN, and the sequence as set forth in SEQ        ID NO: 59 [huCD3-H1L1], respectively.

Also, disclosure provides an antibody, wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the CDR1, CDR2, and        CDR3 sequences of SEQ ID NOs.: 48, 49 and 50, respectively, and        a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NO: 52, DAS and SEQ ID NO: 53,        respectively [226-VH+VL CDR1, -2 and -3 sequences];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55 and 56,        respectively, and a light chain variable region (VL) comprising        CDR1, CDR2, and CDR3 having the sequences as set forth in SEQ ID        NO: 58, the sequence GTN, and the sequence as set forth in SEQ        ID NO: 59 [huCD3-H1L1], respectively.

The antigen binding region that binds to CD3, may bind with anequilibrium dissociation constant K_(D) within the range of 200-1000 nM,such as within the range of 300-1000 nM, within the range of 400-1000nM, within the range of 500-1000 nM, within the range of 300-900 nMwithin the range of 400-900 nM, within the range of 400-700 nM, withinthe range of 500-900 nM, within the range of 500-800 nM, within therange of 500-700 nM, within the range of 600-1000 nM, within the rangeof 600-900 nM, within the range of 600-800 nM, or such as within therange of 600-700 nM.

In further embodiments, the antibody disclosed herein has a lower humanCD3E binding affinity than an antibody having an antigen-binding regioncomprising a VH sequence as set forth in SEQ ID NO: 57, and a VLsequence as set forth in SEQ ID NO: 60 [huCD3-H1L1], preferably whereinsaid affinity is at least 2-fold lower, e.g. at least 5-fold lower, suchas at least 10-fold lower, e.g. at least 20-fold lower, at least 30-foldlower, at least 40-fold lower, at least 45-fold lower, at least 50-foldlower, at least 55-fold lower, or such as at least 60-fold lower.

In particular, the antigen binding region that binds to CD3 may bindwith an equilibrium dissociation constant K_(D) within the range of1-100 nM, such as within the range of 5-100 nM, within the range of10-100 nM, within the range of 1-80 nM, within the range of 1-60 nMwithin the range of 1-40 nM, within the range of 1-20 nM, within therange of 5-80 nM, within the range of 5-60 nM, within the range of 5-40nM, within the range of 5-20 nM, within the range of 10-80 nM, withinthe range of 10-60 nM, within the range of 10-40 nM, or such as withinthe range of 10-20 nM.

The affinity with which the antibody according to the invention bind toCD3 may be determined by biolayer interferometry, using a modificationof the procedure described above or as set forth in Example 2 herein, inwhich the antibody is immobilized on a human IgG Fc Capture biosensorand association and dissociation of the CD3E27-GSKa (mature protein ofSEQ ID NO: 101) to the immobilize antibody is determined. Further, theaffinity with which the antibody according to the invention bind to CD3may be determined by biolayer interferometry as provided in Example 9herein.

Antibodies binding CD3, in particular human CD3, with reduced affinityare provided in WO 2017/009442, and it is to be understood that any ofthese antibodies may serve as the basis for generating antibodiesaccording to the present invention which in addition to the ability tobind 5T4 also have the ability to bind CD3 with reduced affinity. Hence,in further embodiments, the antibody according to the invention is anantibody, wherein

-   -   the antigen binding region that binds to CD3 comprises a heavy        chain variable (VH) region comprising a CDR1 sequence, a CDR2        sequence and a CDR3 sequence,    -   the heavy chain variable (VH) region, when compared to a heavy        chain variable (VH) region comprising the sequence set forth in        SEQ ID NO: 57, has an amino acid substitution in one of the CDR        sequences, the substitution being at a position selected from        the group consisting of: T31, N57, H101, G105, S110 and Y114,        the positions being numbered according to the sequence of SEQ ID        NO: 57; and    -   the wild type light chain variable (VL) region comprises the        CDR1, CDR2 and CDR3 sequences set forth in SEQ ID NOs: 58, GTN        and SEQ ID NO: 59, respectively.

It is preferred that the CDR1, CDR2 and CDR3 sequences of the heavychain variable (VH) region of the antigen binding region that binds toCD3 comprise, in total, at the most 1, 2, 3, 4 or 5 amino acidsubstitutions, when compared to the sequence set forth in SEQ ID NO: 57.

The amino acid sequences of the CDR1, CDR2 and CDR3 of the heavy chainvariable (VH) region of the antigen binding region that binds to CD3 mayhave at least 95% sequence identity, such as at least 96% sequenceidentity, at least 97% sequence identity, at least 98% sequence identityor at least 99% sequence identity to the amino acid sequences of theCDR1, CDR2 and CDR3 of the wild type heavy chain variable (VH) region,sequence identity being calculated based on an aligning an amino acidsequence consisting of the sequences of the CDR1, CDR2 and CDR3 of theheavy chain variable (VH) region of the antigen binding region thatbinds to CD3 with an amino acid sequence comprising the sequences of theCDR1, CDR2 and CDR3 of the wild type heavy chain variable (VH) region.

In particular, the antigen binding region that binds to CD3 may comprisea mutation selected from the group consisting of: T31M, T31P, N57E,H101G, H101N, G105P, S110A, S110G, Y114M, Y114R, Y114V, the positionsbeing numbered according to the reference sequence of SEQ ID NO: 57.

In certain embodiments, the antibody according to the invention is anantibody, wherein when said antibody is a bispecific antibody, which isdevoid of, or has reduced Fc-mediated effector function (“inert”antibody), and comprises an antigen binding region of an antibody thatbinds to CD3, then the antibody:

-   -   a) is capable of mediating concentration-dependent cytotoxicity        of SK-OV-3 cells, when using purified peripheral blood        mononuclear cells (PBMCs) or T cells as effector cells e.g. when        assayed as described in Example 14 herein,    -   b) is capable of mediating concentration-dependent cytotoxicity        of MDA-MB-231 cells, when using purified T cells as effector        cells e.g. when assayed as described in Example 13 herein,    -   c) is capable of activating T cells in vitro in the presence of        MDA-MB-231 tumor cells; e.g. when assayed as described in        Example 13 (II) herein    -   d) is capable of activating T-cells in vitro in the presence of        BxPC-3, PANC-1, Ca Ski and/or SiHa tumor cells; e.g. when        assayed as described in Example 17 herein,    -   e) is capable of inducing cytotoxicity of BxPC-3, PANC-1, Ca Ski        and/or SiHa tumor cells when using purified T cells as effector        cells e.g. when assayed as described in Example 17 herein;        and/or    -   f) shows anti-tumor activity, such as inhibition of tumor growth        or delayed tumor outgrowth, in a humanized immune hematopoietic        stem cell reconstitution mouse xenograft model, such as        NOD.Cg-Prkdc^(scid) II2rg^(tm1Wjl)/SzJ inoculated with human        MDA-MB-231 tumor cells; e.g. when determined as described in        Example 15; and

Further, the antibody according to the invention is an antibody that,when assessed by flow cytometry or ELISA, does not bind leukocyte FcγRs,and does not induce CD3-antibody dependent, FcγR-mediatedCD3-crosslinking in absence of target (5T4)-specific tumor cells bybinding to C1q.

A more detailed disclosure of antibodies with reduced or no Fc-mediatedeffector function (“inert” antibodies) can be found herein below.

The ability of the antibody to mediate concentration-dependentcytotoxicity of SK-OV-3 cells is determined in an in vitro cytotoxicityassay comprising the steps of:

-   -   i) isolating PBMCs or T cells from healthy human donor buffy        coats,    -   ii) providing        -   a first set of samples, wherein each sample comprises PBMCs            and human ovary adenocarcinoma SK-OV-3 cells, and wherein            the ratios PBMCs:SK-OV-3 cells in said samples are 1:2, 1:1,            2:1, 4:1, 8:1, and 12:1; and        -   a second set of samples, wherein each sample comprises T            cells and human ovary adenocarcinoma SK-OV-3 cells and            wherein the ratios of T cells:SK-OV-3 cells in said samples            are 1:2, 1:1, 2:1, 4:1 and 8:1    -   iii) adding the antibody to each set of samples at        concentrations ranging from 0.0128 ng/mL to 1000 ng/mL and        incubating the samples for 72 hours at 37° C.; and then    -   iv) assessing the viability of the SK-OV-3 cells using Resazurin        (7-Hydroxy-3H-phenoxazin-3-one 10-oxide).

The ability to activate T cells in vitro in the presence of MDA-MB-231tumor cells may be determined in an assay comprising the steps of:

-   -   i) Isolating T cells from healthy human donor buffy coats,    -   ii) Providing a set of samples, wherein each sample comprises        T-cells and human breast adenocarcinoma MDA-MB-231 cells and        wherein the ratio of T-cells:MDA-MB-231 cells in said samples is        8:1,    -   iii) adding the antibody to the set of samples at concentrations        ranging from 0.0128 ng/mL to 1000 ng/mL and incubating the        samples for 72 h at 37° C.,    -   iv) staining the Tcells with fluorescent-labeled antibodies        against T-cell activation markers, such as CD69-APC, CD25-PE-Cy7        and CD279/PD 1-BV 604 antibodies, by incubation with said        antibodies for 30 min at 4° C.; and    -   v) analyzing the T cells by flow cytometry.

APC anti-human CD69 (CD69-APC) antibodies are commercially available,for instance from BioLegend (Cat. #s 310909 and 310910). CD25 MonoclonalAntibody, PE-Cyanine7 (CD25-PE-Cy7) is also commercially available, forinstance from ThermoFisher Scientific (Cat. #25-0259-42) and from BDBiosciences (Cat. #557741). Finally, CD279/PD 1-BV 604 antibodies may beobtained commercially from Genscript (Cat. #A01828).

The activation of T cells in vitro in the presence of BxPC-3, PANC-1, CaSki and/or SiHa tumor cells may be determined in an procedure comprisingthe steps of:

-   -   i) Providing T cells isolated from healthy human donor buffy        coats,    -   ii) Providing a set of samples, wherein each sample comprises        said T cells and BxPC-3, PANC-1, Ca Ski or SiHa tumor cells and        wherein the ratio of T cells:tumor cells in said samples is 4:1,    -   iii) adding the antibody to the set of samples at concentrations        ranging from 0.0128 ng/mL to 5000 ng/mL (such as 5-fold        dilutions) and incubating the samples for 72 hours at 37° C.,    -   iv) collecting from each sample 110 μL supernatant containing T        cells and staining the T cells with fluorescent-labeled        antibodies against T-cell markers, such as CD3-eFluor450,        CD4-APC-eFluor780, DC8-AF700, and with antibodies against T-cell        markers, such as 69-APC, CD25-PE-Cy7 and CD279/PD1-BV604        antibodies, by incubation with said antibodies for 30 minutes at        4° C.; and    -   v) analyzing the samples by flow cytometry.

The ability to induce cytotoxicity of BxPC-3, PANC-1, Ca Ski and/or SiHatumor cells may be determined in a procedure comprising the steps of

-   -   i) Providing T cells isolated from healthy human donor buffy        coats,    -   ii) Providing a set of test samples and control samples, wherein        each sample comprises said T-cells and BxPC-3, PANC-1, Ca Ski or        SiHa tumor cells which have been allowed to adhere to the bottom        of a 96-well tissue culture plate and wherein the ratio of        T-cells:tumor cells in said samples is 4:1,    -   iii) adding the antibody to the set of test samples at        concentrations ranging from 0.0128 ng/mL to 5000 ng/mL (such as        5-fold dilutions), while the control samples remain untreated or        are incubated with 5 μM staurosporin, and incubating all samples        for 72 hours at 37° C.,    -   iv) Incubating the adherent cells in 10% (w/w)        7-hydroxy-3H-phenoxazin-3-one 10-oxide (Resazurin) in RPMI-1640        medium supplemented with 10% (w/w) donor bovine serum with iron        and penicillin/streptomycin at 37° C. for 4 hours,    -   v) Measuring the absorbance of the cells; setting the absorbance        of the cells incubated with staurosporin as 0% viability and the        untreated cells as 100% viability and calculating the percentage        viable cells as        ×100% viable cells=([absorbance sample−absorbance staurosporine        treated cells]/[absorbance untreated cells−absorbance        staurosporine treated cells])

The antibody of the invention may in particular be an antibody, whereinthe antigen-binding region capable of binding to CD3 comprises:

-   -   a) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 61, 55,        and 56 [VH CDR1-T31P+Wild type VH CDRs 2,3], respectively, and a        light chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], or    -   b) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 63, 55,        and 56 [VH CDR1-T31M+Wild type VH CDRs 2,3], respectively, and a        light chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively, or    -   c) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 65,        and 56 [VH CDR-N57E+Wild type VH CDRs 1,3], respectively, and a        light chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively, or    -   d) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 67 [Wild type VH CDRs 1,2+VH CDR3-H101G], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively.    -   e) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 69 [Wild type VH CDRs 1,2+VH CDR3-H101N], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively;    -   f) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 71 [Wild type VH CDRs 1,2+VH CDR3-G105P], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively;    -   g) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 73 [Wild type VH CDRs 1,2+VH CDR3-S110A], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively, or    -   h) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 75 [Wild type VH CDRs 1,2+VH CDR3-S110G], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively,    -   i) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 77 [Wild type VH CDRs 1,2+VH CDR3-Y114V], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively, or    -   j) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 79 [Wild type VH CDRs 1,2+VH CDR3-Y114M], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and

CDR3 having the sequences as set forth in SEQ ID NO: 58, the sequenceGTN, and the sequence as set forth in SEQ ID NO: 59, respectively [Wildtype VL CDRs 1,2,3], respectively, or

-   -   k) a heavy chain variable region (VH) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NOs: 54, 55,        and 81 [Wild type VH CDRs 1,2+VH CDR3-Y114R], respectively, and        a light chain variable region (VL) comprising CDR1, CDR2, and        CDR3 having the sequences as set forth in SEQ ID NO: 58, the        sequence GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively.

In certain embodiments, the antigen-binding region capable of binding toCD3 a heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3having the sequences as set forth in SEQ ID NOs: 54, 55, and 67 [Wildtype VH CDRs 1,2+VH CDR3-H101G], respectively, and a light chainvariable region (VL) comprising CDR1, CDR2, and CDR3 having thesequences as set forth in SEQ ID NO: 58, the sequence GTN, and thesequence as set forth in SEQ ID NO: 59, respectively [Wild type VL CDRs1,2,3], respectively.

Further, the present invention provides an antibody as defined above,wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        sequences of SEQ ID NOs.: 6, 7 and 8, respectively, and a light        chain variable region (VL) comprising the CDR1, CDR2, and CDR3        sequences of SEQ ID NO: 10, AAS and SEQ ID NO: 11, respectively        [059];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55, and 67        [Wild type VH CDRs 1,2+VH CDR3-H101G], respectively, and a light        chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively.

Also, the invention provides an antibody as defined above, wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the CDR1, CDR2, and        CDR3 sequences of SEQ ID NOs.: 41, 42 and 43, respectively, and        a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NO: 45, DAS and 46, respectively        [207];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55, and 67        [Wild type VH CDRs 1,2+VH CDR3-H101G], respectively, and a light        chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively.

Further, the invention provides an antibody as defined above, wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the CDR1, CDR2, and        CDR3 sequences of SEQ ID NOs.: 48, 49 and 50, respectively, and        a light chain variable region (VL) comprising the CDR1, CDR2,        and CDR3 sequences of SEQ ID NO: 52, DAS and 53, respectively        [226];

and

-   -   the antigen-binding region capable of binding to CD3 comprises a        heavy chain variable region (VH) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NOs: 54, 55, and 67        [Wild type VH CDRs 1,2+VH CDR3-H101G], respectively, and a light        chain variable region (VL) comprising CDR1, CDR2, and CDR3        having the sequences as set forth in SEQ ID NO: 58, the sequence        GTN, and the sequence as set forth in SEQ ID NO: 59,        respectively [Wild type VL CDRs 1,2,3], respectively.

In the antibody according to the invention, the antigen-binding regioncapable of binding to human CD3 may comprise a VH sequence and a VLsequence selected from the group consisting of:

-   -   a) a VH sequence as set forth in SEQ ID NO: 62 [VH T31P] and a        VL sequence as set forth in SEQ ID NO: 60,    -   b) a VH sequence as set forth in SEQ ID NO: 64 [VH T31M] and a        VL sequence as set forth in SEQ ID NO: 60,    -   c) a VH sequence as set forth in SEQ ID NO: 66 [VH N57E] and a        VL sequence as set forth in SEQ ID NO: 60,    -   d) a VH sequence as set forth in SEQ ID NO: 68 [VH H101G] and a        VL sequence as set forth in SEQ ID NO: 60,    -   e) a VH sequence as set forth in SEQ ID NO: 70 [VH H101N] and a        VL sequence as set forth in SEQ ID NO: 60,    -   f) a VH sequence as set forth in SEQ ID NO: 72 [VH G105P] and a        VL sequence as set forth in SEQ ID NO: 60,    -   g) a VH sequence as set forth in SEQ ID NO: 74 [VH S110A] and a        VL sequence as set forth in SEQ ID NO: 60,    -   h) a VH sequence as set forth in SEQ ID NO: 76 [VH S110G] and a        VL sequence as set forth in SEQ ID NO: 60,    -   i) a VH sequence as set forth in SEQ ID NO: 78 [VH Y114V] and a        VL sequence as set forth in SEQ ID NO: 60,    -   j) a VH sequence as set forth in SEQ ID NO: 80 [VH Y114M] and a        VL sequence as set forth in SEQ ID NO: 60; and    -   k) a VH sequence as set forth in SEQ ID NO: 82 [VH Y114R] and a        VL sequence as set forth in SEQ ID NO: 60.

In particular, the antibody according to the invention may be anantibody, wherein the antigen-binding region capable of binding to humanCD3 comprises a VH sequence as set forth in SEQ ID NO: 68 [VH H101G] anda VL sequence as set forth in SEQ ID NO: 60.

In some embodiments, the antibody according to the invention is one,wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the sequence of SEQ        ID NO: 5 or a sequence having at least 90%, at least 95%, at        least 97%, or at least 99% amino acid sequence identity to the        sequence of SEQ ID NO: 5 [059];

and

-   -   the antigen-binding region capable of binding to human CD3        comprises a VH sequence as set forth in SEQ ID NO: 68 [VH H101G]        and a VL sequence as set forth in SEQ ID NO: 60.

In other embodiments, the antibody according to the invention is one,wherein

-   -   the antigen-binding region capable of binding to 5T4 comprises a        heavy chain variable region (VH) comprising the sequence of SEQ        ID NO: 40 or a sequence having at least 90%, at least 95%, at        least 97%, or at least 99% amino acid sequence identity to the        sequence of SEQ ID NO: 40 [207];

and

-   -   the antigen-binding region capable of binding to human CD3        comprises a VH sequence as set forth in SEQ ID NO: 68 [VH H101G]        and a VL sequence as set forth in SEQ ID NO: 60.

In still other embodiments, the antibody according to the invention isone, wherein the antigen-binding region capable of binding to 5T4comprises a heavy chain variable region (VH) comprising the sequence ofSEQ ID NO: 47 or a sequence having at least 90%, at least 95%, at least97%, or at least 99% amino acid sequence identity to the sequence of SEQID NO: 47 [226];

and the antigen-binding region capable of binding to human CD3 comprisesa VH sequence as set forth in SEQ ID NO: 68 [VH H101G] and a VL sequenceas set forth in SEQ ID NO: 60.

As will be well-known to the skilled person, each antigen-binding regionof an antibody generally comprises a heavy chain variable region (VH)and a light chain variable region (VL), and each of the variable regionscomprises three CDR sequences, CDR1, CDR2 and CDR3, respectively, andfour framework sequences, FR1, FR2, FR3 and FR4, respectively. Thisstructure may also be found in the antibodies according to the presentinvention. Further, the antibodies according to the invention maycomprise two heavy chain constant regions (CH), and two light chainconstant regions (CL).

In particular embodiments, the antibody according to the inventioncomprises a first and a second heavy chain, such as a first and secondheavy chain each comprising at least a hinge region, a CH2 and CH3region. Stable, heterodimeric antibodies can be obtained at high yieldfor instance by so-called Fab-arm exchange as provided in WO 2008/119353and WO 2011/131746, on the basis of two homodimeric starting proteinscontaining only a few, asymmetrical mutations in the CH3 regions. Hence,in some embodiments of the invention, the antibody a first heavy chainwherein at least one of the amino acids at the positions correspondingto positions selected from the group consisting of T366, L368, K370,D399, F405, Y407 and K409 in a human IgG1 heavy chain has beensubstituted, and a second heavy chain wherein at least one of the aminoacids in the positions corresponding to a position selected from thegroup consisting of T366, L368, K370, D399, F405, Y407, and K409 in ahuman IgG1 heavy chain has been substituted, wherein said substitutionsof said first and said second heavy chains are not in the samepositions, and wherein the amino acid positions are numbered accordingto EU numbering.

In particular embodiments, the invention provides an antibody, whereinthe amino acid in the position corresponding to K409 in a human IgG1heavy chain is R in said first heavy chain, and the amino acid in theposition corresponding to F405 in a human IgG1 heavy chain is L in saidsecond heavy chain, or vice versa.

In some embodiments, the antibody according to the present inventioncomprises, in addition to the antigen-binding regions, an Fc regionconsisting of the Fc sequences of the two heavy chains. The first andsecond Fc sequence may each be of any isotype, including any humanisotype, such as an IgG1, IgG2, IgG3, IgG4, IgE, IgD, IgM, or IgAisotype or a mixed isotype. Preferably, the Fc region is a human IgG1,IgG2, IgG3, IgG4 isotype or a mixed isotype, such as a human IgG1isotype.

Antibodies according to the present invention may comprise modificationsin the Fc region to render the antibody an inert, or non-activating,antibody. Hence, in the antibodies disclosed herein, one or both heavychains may be modified so that the antibody induces Fc-mediated effectorfunction to a lesser extent relative to an antibody which is identical,except for comprising non-modified first and second heavy chains. TheFc-mediated effector function may be measured by determining Fc-mediatedCD69 expression on T cells (i.e. CD69 expression as a result of CD3antibody-mediated, Fcγ receptor-dependent CD3 crosslinking), by bindingto Fcγ receptors, by binding to C1q, or by induction of Fc-mediatedcross-linking of FcγRs. In particular, the heavy chain constantsequences may be modified so that the Fc-mediated CD69 expression isreduced by at least 50%, at least 60%, at least 70%, at least 80%, atleast 90%, at least 99% or 100% when compared to a wild-type(unmodified) antibody, wherein said Fc-mediated CD69 expression isdetermined in a PBMC-based functional assay, e.g. as described inExample 3 of WO2015001085. Modifications of the heavy and light chainconstant sequences may also result in reduced binding of C1q to saidantibody. As compared to an unmodified antibody the reduction may be byat least 70%, at least 80%, at least 90%, at least 95%, at least 97%, or100% and the C1q binding may be determined by ELISA. Further, the Fcregion which may be modified so that said antibody mediates reducedFc-mediated T-cell proliferation compared to an unmodified antibody byat least 50%, at least 60%, at least 70%, at least 80%, at least 90%, atleast 99% or 100%, wherein said T-cell proliferation is measured in aPBMC-based functional assay.

Examples of amino acid positions that may be modified, e.g. in an IgG1isotype antibody, include positions L234 and L235. Hence, the antibodyaccording to the invention may comprises a first and a second heavychain, and wherein in both the first and the second heavy chain, theamino acid residues at the positions corresponding to positions L234 andL235 in a human IgG1 heavy chain according to EU numbering are F and E,respectively.

In addition, a D265A amino acid substitution can decrease binding to allFcγ receptors and prevent ADCC (Shields et al., 2001, J. Biol. Chem.(276):6591-604). Therefore, the antibody according to the invention maycomprise a first and a second heavy chain, wherein in both the first andthe second heavy chain, the amino acid residue at the positioncorresponding to position D265 in a human IgG1 heavy chain according toEU numbering is A. Further embodiments of the invention provideantibodies wherein, in at least one, such as in both, of said first andsecond heavy chains the amino acids in the positions corresponding topositions L234, L235, and D265 in a human IgG1 heavy chain, are F, E,and A, respectively. In the present application antibodies, which havethe combination of three amino acid substitutions L234F, L235E and D265Aand in addition the K409R or the F405L mutation disclosed herein aboveare termed with the suffix “FEAR” or “FEAL”, respectively.

The amino acid sequence of the wild type IgG1 heavy chain constantregion is identified herein as SEQ ID NO: 89. Consistent with theembodiments disclosed above, the antibody of the invention may comprisean IgG1 heavy chain constant region carrying the F405L substitution andhaving the amino acid sequence set forth in SEQ ID NO: 90 and/or an IgG1heavy chain constant region carrying the K409R substitution and havingthe amino acid sequence set forth in SEQ ID NO: 94.

The amino acid sequence of an IgG1 heavy chain constant region carryingthe L234F, L235E and D265A substitutions is identified herein as SEQ IDNO: 91. The amino acid sequence of an IgG1 heavy chain constant regioncarrying the L234F, L235E, D265A and F405L substitutions is identifiedherein as SEQ ID NO: 92. The amino acid sequence of an IgG1 heavy chainconstant region carrying the L234F, L235E, D265A and K409R substitutionsis identified herein as SEQ ID NO: 93.

The present invention further provides an antibody, wherein

-   -   a) the antigen-binding region(s) capable of binding to 5T4        is/are humanized, and/or    -   b) the antigen-binding region capable of binding to CD3, if        present, is humanized.

Also, the invention provides an antibody, wherein

-   -   a) the antigen-binding region(s) capable of binding to 5T4        is/are human, and/or    -   b) the antigen-binding region capable of binding to CD3, if        present, is human.

Further, the invention provides an antibody, wherein

-   -   a) the antigen-binding region(s) capable of binding to 5T4        is/are chimeric, and/or    -   b) the antigen-binding region capable of binding to CD3, if        present, is chimeric.

In some embodiments of the invention, the antibody comprises a kappa (κ)light chain. The sequence of in particular embodiments of the inventionconcerning bispecific antibodies, the kappa light chain comprises theCDR1, -2 and -3 sequences of a 5T4 antibody light chain as disclosedabove.

In further embodiments of the invention, the antibody according to anyone of the preceding claims, wherein said antibody comprises a lambda(A) light chain. In particular embodiments of the invention concerningbispecific antibodies, the lambda light chain comprises the CDR1, -2 and-3 sequences of a CD3 antibody light chain as disclosed above, inparticular a the CDR1, -2 and -3 sequences of a CD3 antibody havingreduced affinity for CD3 as disclosed above. The amino acid sequence ofa kappa light chain constant region is included herein as SEQ ID NO: 95and the amino acid sequence of a lambda light chain constant region isincluded herein as SEQ ID NO: 96.

In particular embodiments, the antibody comprises a lambda (A) lightchain and a kappa (κ) light chain; e.g. an antibody with a heavy chainand a lambda light chain which comprise the binding region capable ofbinding to CD3, and a heavy chain and a kappa light chain which comprisethe binding region capable of binding to 5T4.

Immunoconjugates

In another aspect, the invention provides an immunoconjugate orantibody-drug conjugate (ADC) comprising the antibody defined above, anda therapeutic moiety, such as a cytotoxic agent, a chemotherapeuticdrug, a cytokine, an immunosuppressant, antibiotic, or a radioisotope.In general, the skilled person will have at his disposition numerouscytotoxic agents, chemotherapeutic drugs, cytokines, immunosuppressants,antibiotics and radioisotopes, the optimal choice of therapeutic moietydepending on the desired application of the immunoconjugate. For certainapplications the preferred cytotoxic agent may be amicrotubule-disrupting agent, such as a duostatin, e.g. Duostatin-3.

Nucleic Acid Constructs

A further aspect of the invention provides nucleic acid constructcomprising

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein before, and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein before.

The nucleic acid construct may further comprise

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to CD3 as defined herein before; and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to CD3 as defined herein before.        Expression Vectors

Another aspect of the invention provides an expression vector comprisingnucleic acid sequences encoding heavy and/or light chain sequences of anantibody according to the invention. In particular, the expressionvector may comprise:

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein before, and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to 5T4 as defined herein before.

The expression vector may further comprise:

-   -   a) a nucleic acid sequence encoding a heavy chain sequence of an        antibody comprising an antigen-binding region capable of binding        to CD3 as defined herein before; and/or    -   b) a nucleic acid sequence encoding a light chain sequence of an        antibody comprising an antigen-binding region capable of binding        to CD3 as defined herein before.

In a further embodiment, the expression vector further comprises anucleic acid sequence encoding the constant region of a light chain, aheavy chain or both light and heavy chains of an antibody, e.g. a humanIgG1,κ monoclonal antibody.

An expression vector in the context of the present invention may be anysuitable vector, including chromosomal, non-chromosomal, and syntheticnucleic acid vectors (a nucleic acid sequence comprising a suitable setof expression control elements). Examples of such vectors includederivatives of SV40, bacterial plasmids, phage DNA, baculovirus, yeastplasmids, vectors derived from combinations of plasmids and phage DNA,and viral nucleic acid (RNA or DNA) vectors. In one embodiment, ananti-5T4 antibody-encoding nucleic acid is comprised in a naked DNA orRNA vector, including, for example, a linear expression element (asdescribed in for instance Sykes and Johnston, Nat Biotech 17, 355-59(1997)), a compacted nucleic acid vector (as described in for instanceU.S. Pat. No. 6,077,835 and/or WO 00/70087), a plasmid vector such aspBR322, pUC 19/18, or pUC 118/119, a “midge” minimally-sized nucleicacid vector (as described in for instance Schakowski et al., Mol Ther 3,793-800 (2001)), or as a precipitated nucleic acid vector construct,such as a CaP04-precipitated construct (as described in for instance WO00/46147, Benvenisty and Reshef, PNAS USA 83, 9551-55 (1986), Wigler etal., Cell 14, 725 (1978), and Coraro and Pearson, Somatic Cell Genetics7, 603 (1981)). Such nucleic acid vectors and the usage thereof are wellknown in the art (see for instance U.S. Pat. Nos. 5,589,466 and5,973,972).

In one embodiment, the vector is suitable for expression of the anti-5T4antibody in a bacterial cell. Examples of such vectors includeexpression vectors such as BlueScript (Stratagene), pIN vectors VanHeeke & Schuster, J Biol Chem 264, 5503 5509 (1989), pET vectors(Novagen, Madison Wis.) and the like).

An expression vector may also or alternatively be a vector suitable forexpression in a yeast system. Any vector suitable for expression in ayeast system may be employed. Suitable vectors include, for example,vectors comprising constitutive or inducible promoters such as alphafactor, alcohol oxidase and PGH (reviewed in: F. Ausubel et al., ed.Current Protocols in Molecular Biology, Greene Publishing and WileyInterScience New York (1987), and Grant et al., Methods in Enzymol 153,516 544 (1987)).

A nucleic acid construct and/or vector may also comprises a nucleic acidsequence encoding a secretion/localization sequence, which can target apolypeptide, such as a nascent polypeptide chain, to the periplasmicspace or into cell culture media. Such sequences are known in the art,and include secretion leader or signal peptides, organelle targetingsequences (e. g., nuclear localization sequences, ER retention signals,mitochondrial transit sequences, chloroplast transit sequences),membrane localization/anchor sequences (e. g., stop transfer sequences,GPI anchor sequences), and the like.

In an expression vector of the invention, anti-5T4 antibody-encodingnucleic acids may comprise or be associated with any suitable promoter,enhancer, and other expression-facilitating elements. Examples of suchelements include strong expression promoters (e.g., human CMV IEpromoter/enhancer as well as RSV, SV40, SL3-3, MMTV, and HIV LTRpromoters), effective poly (A) termination sequences, an origin ofreplication for plasmid product in E. coli, an antibiotic resistancegene as selectable marker, and/or a convenient cloning site (e.g., apolylinker). Nucleic acids may also comprise an inducible promoter asopposed to a constitutive promoter such as CMV IE (the skilled artisanwill recognize that such terms are actually descriptors of a degree ofgene expression under certain conditions).

In one embodiment, the anti-5T4-antibody-encoding expression vector maybe positioned in and/or delivered to a host cell or host animal via aviral vector.

Cells and Host Cells

In a further aspect, the invention provides a cell comprising a nucleicacid construct as defined herein above, or an expression vector asdefined herein above. It is to be understood that the cell may have beenobtained by transfecting a host cell with said nucleic acid construct orexpression vector, such as a recombinant host cell.

The host cell may be of human origin, such as a human embryonic kidney(HEK) cell, such as a HEK/Expi cell. Alternatively, it may be of rodentorigin, such as a Chinese hamster ovary cell, such as a CHO/N50 cell.Further, the host cell may be of bacterial origin.

The cell may comprise a nucleic acid sequence encoding an antibody ofthe invention or parts thereof stably integrated into the cellulargenome. Alternatively, the cell may comprise a non-integrated nucleicacid, such as a plasmid, cosmid, phagemid, or linear expression element,which comprises a sequence coding for expression of an anti-5T4 antibodyof the invention or a part thereof. In particular, the host cell maycomprise a non-integrated nucleic acid, such as a plasmid, cosmid,phagemid, or linear expression element, which comprises a sequencecoding for expression of an anti-5T4 antibody or a part thereof.

Compositions

A still further aspect of the invention provides a compositioncomprising an antibody; e.g. a bispecific antibody or an immunoconjugateas defined in the above. The composition may be a pharmaceuticalcomposition comprising the antibody, bispecific antibody orimmunoconjugate and a pharmaceutically acceptable carrier.

The pharmaceutical compositions may be formulated with the carrier,excipient and/or diluent as well as any other components suitable forpharmaceutical compositions, including known adjuvants, in accordancewith conventional techniques such as those disclosed in Remington: TheScience and Practice of Pharmacy, 19th Edition, Gennaro, Ed., MackPublishing Co., Easton, Pa., 1995. The pharmaceutically acceptablecarriers or diluents as well as any known adjuvants and excipientsshould be suitable for the antibody or antibody conjugate of the presentinvention and the chosen mode of administration. Suitability forcarriers and other components of pharmaceutical compositions isdetermined based on the lack of significant negative impact on thedesired biological properties of the chosen compound or pharmaceuticalcomposition of the present invention (e.g., less than a substantialimpact [10% or less relative inhibition, 5% or less relative inhibition,etc.] upon antigen binding).

A pharmaceutical composition of the present invention may includediluents, fillers, salts, buffers, detergents (e. g., a nonionicdetergent, such as Tween-20 or Tween-80), stabilizers (e.g., sugars orprotein-free amino acids), preservatives, tissue fixatives,solubilizers, and/or other materials suitable for inclusion in apharmaceutical composition.

The actual dosage levels of the active ingredients in the pharmaceuticalcompositions of the present invention may be varied so as to obtain anamount of the active ingredient which is effective to achieve thedesired therapeutic response for a particular patient, composition, andmode of administration, without being toxic to the patient. The selecteddosage level will depend upon a variety of pharmacokinetic factorsincluding the activity of the particular compositions of the presentinvention employed, or the amide thereof, the route of administration,the time of administration, the rate of excretion of the particularcompound being employed, the duration of the treatment, other drugs,compounds and/or materials used in combination with the particularcompositions employed, the age, sex, weight, condition, general healthand prior medical history of the patient being treated, and like factorswell known in the medical arts.

Pharmaceutically acceptable carriers include any and all suitablesolvents, dispersion media, coatings, antibacterial and antifungalagents, isotonicity agents, antioxidants and absorption-delaying agents,and the like that are physiologically compatible with a compound of thepresent invention.

Examples of suitable aqueous and non-aqueous carriers which may beemployed in the pharmaceutical compositions of the present inventioninclude water, saline, phosphate buffered saline, ethanol, dextrose,polyols (such as glycerol, propylene glycol, polyethylene glycol, andthe like), and suitable mixtures thereof, vegetable oils, such as oliveoil, corn oil, peanut oil, cottonseed oil, and sesame oil, carboxymethylcellulose colloidal solutions, tragacanth gum and injectable organicesters, such as ethyl oleate, and/or various buffers. Other carriers arewell known in the pharmaceutical arts.

Pharmaceutically acceptable carriers include sterile aqueous solutionsor dispersions and sterile powders for the extemporaneous preparation ofsterile injectable solutions or dispersion. The use of such media andagents for pharmaceutically active substances is known in the art.Except insofar as any conventional media or agent is incompatible withthe active compound, use thereof in the pharmaceutical compositions ofthe present invention is contemplated.

Pharmaceutical compositions of the present invention may also comprisepharmaceutically acceptable antioxidants for instance (1) water-solubleantioxidants, such as ascorbic acid, cysteine hydrochloride, sodiumbisulfate, sodium metabisulfite, sodium sulfite and the like; (2)oil-soluble antioxidants, such as ascorbyl palmitate, butylatedhydroxyanisole (BHA), butylated hydroxytoluene (BHT), lecithin, propylgallate, alpha-tocopherol, and the like; and (3) metal-chelating agents,such as citric acid, ethylenediamine tetraacetic acid (EDTA), sorbitol,tartaric acid, phosphoric acid, and the like.

Pharmaceutical compositions of the present invention may also compriseisotonicity agents, such as sugars, polyalcohols, such as mannitol,sorbitol, glycerol or sodium chloride in the compositions.

The pharmaceutical compositions of the present invention may alsocontain one or more adjuvants appropriate for the chosen route ofadministration such as preservatives, wetting agents, emulsifyingagents, dispersing agents, preservatives or buffers, which may enhancethe shelf life or effectiveness of the pharmaceutical composition. Thecompounds of the present invention may be prepared with carriers thatwill protect the compound against rapid release, such as a controlledrelease formulation, including implants, transdermal patches, andmicro-encapsulated delivery systems. Such carriers may include gelatin,glyceryl monostearate, glyceryl distearate, biodegradable, biocompatiblepolymers such as ethylene vinyl acetate, polyanhydrides, polyglycolicacid, collagen, poly-ortho esters, and polylactic acid alone or with awax, or other materials well known in the art. Methods for thepreparation of such formulations are generally known to those skilled inthe art, see e.g. Sustained and Controlled Release Drug DeliverySystems, J. R. Robinson, ed., Marcel Dekker, Inc., New York, 1978.

In one embodiment, the compounds of the present invention may beformulated to ensure proper distribution in vivo. Pharmaceuticallyacceptable carriers for parenteral administration include sterileaqueous solutions or dispersions and sterile powders for theextemporaneous preparation of sterile injectable solutions ordispersion. The use of such media and agents for pharmaceutically activesubstances is known in the art. Except in so far as any conventionalmedia or agent is incompatible with the active compound, use thereof inthe pharmaceutical compositions of the present invention iscontemplated. Other active or therapeutic compounds may also beincorporated into the compositions.

Pharmaceutical compositions for injection must typically be sterile andstable under the conditions of manufacture and storage. The compositionmay be formulated as a solution, micro-emulsion, liposome, or otherordered structure suitable to high drug concentration. The carrier maybe an aqueous or a non-aqueous solvent or dispersion medium containingfor instance water, ethanol, polyols (such as glycerol, propyleneglycol, polyethylene glycol, and the like), and suitable mixturesthereof, vegetable oils, such as olive oil, and injectable organicesters, such as ethyl oleate. The proper fluidity may be maintained, forexample, by the use of a coating such as lecithin, by the maintenance ofthe required particle size in the case of dispersion and by the use ofsurfactants. In many cases, it will be preferable to include isotonicagents, for example, sugars, polyalcohols such as glycerol, mannitol,sorbitol, or sodium chloride in the composition. Prolonged absorption ofthe injectable compositions may be brought about by including in thecomposition an agent that delays absorption, for example, monostearatesalts and gelatin. Sterile injectable solutions may be prepared byincorporating the active compound in the required amount in anappropriate solvent with one or a combination of ingredients e.g. asenumerated above, as required, followed by sterilizationmicrofiltration. Generally, dispersions are prepared by incorporatingthe active compound into a sterile vehicle that contains a basicdispersion medium and the required other ingredients e.g. from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, examples of methods of preparation arevacuum drying and freeze-drying (lyophilization) that yield a powder ofthe active ingredient plus any additional desired ingredient from apreviously sterile-filtered solution thereof.

Sterile injectable solutions may be prepared by incorporating the activecompound in the required amount in an appropriate solvent with one or acombination of ingredients enumerated above, as required, followed bysterilization microfiltration. Generally, dispersions are prepared byincorporating the active compound into a sterile vehicle that contains abasic dispersion medium and the required other ingredients from thoseenumerated above. In the case of sterile powders for the preparation ofsterile injectable solutions, examples of methods of preparation arevacuum-drying and freeze-drying (lyophilization) that yield a powder ofthe active ingredient plus any additional desired ingredient from apreviously sterile-filtered solution thereof.

The pharmaceutical composition of the present invention may contain oneantibody, bispecific antibody or antibody-drug conjugate (ADC) of thepresent invention, a combination of an antibody, a bispecific antibodyor ADC according to the invention with another therapeutic compound, ora combination of compounds of the present invention.

The pharmaceutical composition may be administered by any suitable routeand mode. Suitable routes of administering a compound of the presentinvention in vivo and in vitro are well known in the art and may beselected by those of ordinary skill in the art.

In one embodiment, the pharmaceutical composition of the presentinvention is administered parenterally; i.e. by a mode of administrationother than enteral and topical administration; usually by injection, andinclude epidermal, intravenous, intramuscular, intra-arterial,intrathecal, intracapsular, intra-orbital, intracardiac, intradermal,intraperitoneal, intratendinous, transtracheal, subcutaneous,subcuticular, intra-articular, subcapsular, subarachnoid, intraspinal,intracranial, intrathoracic, epidural and intrasternal injection andinfusion. In particular, the pharmaceutical composition of the presentinvention may be administered by intravenous or subcutaneous injectionor infusion.

Uses and Therapeutical Applications

The present invention further provides an antibody, such as a bispecificantibody, or an immunoconjugate or antibody-drug conjugate (ADC) asdefined herein for use as a medicament. The anti-5T4 antibodies orimmunoconjugates of the present invention can be used in the treatmentor prevention of a disease or disorder involving cells expressing 5T4.In particular, the bispecific antibodies according to the invention;i.e. antibodies which comprise antigen binding regions capable ofbinding 5T4 and CD3 may be useful in therapeutic settings in whichspecific targeting and T cell-mediated killing of cells that express 5T4is desired, and they may be more efficient compared to a regularanti-5T4 antibody in certain such indications and settings.

In one embodiment, the antibody, such as the bispecific antibody, orimmunoconjugate or antibody-drug conjugate (ADC) of the presentinvention is disclosed herein for use in the treatment of cancer. Theantibody, such as the bispecific antibody, or the immunoconjugate orantibody-drug conjugate (ADC) may in particular be use in treatment of acancer, wherein the cancer is characterized by expression of 5T4 in atleast some of the tumor cells.

The cancer may in particular be selected from the group consisting ofkidney/renal cancer, breast cancer, colorectal cancer, prostate cancer,ovarian cancer, bladder cancer, uterine/endometrial/cervical cancer,lung cancer, gastro-intestinal cancer, stomach cancer, pancreaticcancer, thyroid cancer, head and neck cancer, lymphoma, acute myeloidleukemia.

Additionally, the invention relates to the use of an antibody accordingto the invention for the manufacture of a medicament, such as amedicament for the treatment of cancer, e.g. a cancer selected from thegroup consisting of kidney/renal cancer, breast cancer, colorectalcancer, prostate cancer, ovarian cancer, bladder cancer,uterine/endometrial/cervical cancer, lung cancer, gastro-intestinalcancer, stomach cancer, pancreatic cancer, thyroid cancer, head and neckcancer, lymphoma, acute myeloid leukemia.

In a further aspect, the invention provides method of treating adisease, the method comprising administering an antibody, animmunoconjugate, a composition, such as a pharmaceutical composition orantibody-drug conjugate (ADC) according to the invention to a subject inneed thereof.

In particular embodiments of the invention, said method is for treatmentof a cancer. The method of the invention may in particular comprise thesteps of:

-   -   a) selecting a subject suffering from a cancer comprising tumor        cells expressing 5T4 and/or a cancer known to express 5T4; and    -   b) administering to the subject the antibody, such as the        bispecific antibody, the pharmaceutical composition or the        antibody-drug conjugate (ADC) of the present invention.

The cancer may in particular be selected from the group consisting ofkidney/renal cancer, breast cancer, colorectal cancer, prostate cancer,ovarian cancer, bladder cancer, uterine/endometrial/cervical cancer,lung cancer, gastro-intestinal cancer, stomach cancer, pancreaticcancer, thyroid cancer, head and neck cancer, lymphoma, acute myeloidleukemia.

Dosage regimens in the above methods of treatment and uses are adjustedto provide the optimum desired response (e.g., a therapeutic response).For example, a single bolus may be administered, several divided dosesmay be administered over time or the dose may be proportionally reducedor increased as indicated by the exigencies of the therapeuticsituation. Parenteral compositions may be formulated in dosage unit formfor ease of administration and uniformity of dosage.

The efficient dosages and the dosage regimens for the antibodies dependon the disease or condition to be treated and may be determined by thepersons skilled in the art. An exemplary, non-limiting range for atherapeutically effective amount of a compound of the present inventionis about 0.001-10 mg/kg, such as about 0.001-5 mg/kg, for example about0.001-2 mg/kg, such as about 0.001-1 mg/kg, for instance about 0.001,about 0.01, about 0.1, about 1 or about 10 mg/kg. Another exemplary,non-limiting range for a therapeutically effective amount of an antibodyof the present invention is about 0.1-100 mg/kg, such as about 0.1-50mg/kg, for example about 0.1-20 mg/kg, such as about 0.1-10 mg/kg, forinstance about 0.5, about such as 0.3, about 1, about 3, about 5, orabout 8 mg/kg.

A physician having ordinary skill in the art may readily determine andprescribe the effective amount of the pharmaceutical compositionrequired. For example, the physician or veterinarian could start dosesof the antibody employed in the pharmaceutical composition at levelslower than that required to achieve the desired therapeutic effect andgradually increase the dosage until the desired effect is achieved. Ingeneral, a suitable daily dose of an antibody of the present inventionwill be that amount of the compound which is the lowest dose effectiveto produce a therapeutic effect. Administration may e.g. be parenteral,such as intravenous, intramuscular or subcutaneous. In one embodiment,the antibodies may be administered by infusion in a weekly dosage ofcalculated by mg/m2. Such dosages can, for example, be based on themg/kg dosages provided above according to the following: dose(mg/kg)×70:1.8. Such administration may be repeated, e.g., 1 to 8 times,such as 3 to 5 times. The administration may be performed by continuousinfusion over a period of from 2 to 24 hours, such as from 2 to 12hours. In one embodiment, the antibodies may be administered by slowcontinuous infusion over a long period, such as more than 24 hours, toreduce toxic side effects.

In one embodiment, the antibodies may be administered in a weekly dosageof calculated as a fixed dose for up to 8 times, such as from 4 to 6times when given once a week. Such regimen may be repeated one or moretimes as necessary, for example, after 6 months or 12 months. Such fixeddosages can, for example, be based on the mg/kg dosages provided above,with a body weight estimate of 70 kg. The dosage may be determined oradjusted by measuring the amount of antibody of the present invention inthe blood upon administration by for instance taking out a biologicalsample and using anti-idiotypic antibodies which target the 5T4 antigenantigen-binding region of the antibodies of the present invention.

In one embodiment, the antibodies may be administered as maintenancetherapy, such as, e.g., once a week for a period of 6 months or more.

An antibody may also be administered prophylactically to reduce the riskof developing cancer, delay the onset of the occurrence of an event incancer progression, and/or reduce the risk of recurrence when a canceris in remission.

The antibodies of the invention may also be administered in combinationtherapy, i.e., combined with other therapeutic agents relevant for thedisease or condition to be treated. Accordingly, in one embodiment, theantibody-containing medicament is for combination with one or morefurther therapeutic agents, such as a cytotoxic, chemotherapeutic oranti-angiogenic agent.

Antibody Production

Also provided herein is a method for producing the antibody, such as thebispecific antibody of the invention. In particular, there is provided amethod for producing the antibody of the invention, comprising the stepsof

-   -   a) culturing a host cell comprising an expression vector as        defined herein; and    -   b) and purifying said antibody from the culture medium.

In embodiments of the invention, wherein the antibody comprises abinding region capable of binding to 5T4 and a binding region capable ofbinding to CD3, the antibody may be produced using a method comprisingthe steps of

-   -   a) Providing an antibody capable of binding to 5T4 by culturing        a host cell comprising an expression vector as defined herein        under conditions allowing expression of the antibody capable of        binding to 5T4, and purifying the antibody capable of binding to        5T4 from the culture medium;    -   b) Providing an antibody capable of binding to CD3 by culturing        a host cell comprising an expression vector comprising        -   I) a nucleic acid sequence encoding a heavy chain sequence            of an antibody comprising an antigen-binding region capable            of binding to CD3 as defined herein above; and        -   II) a nucleic acid sequence encoding a light chain sequence            of an antibody comprising an antigen-binding region capable            of binding to CD3 as defined herein above;    -   under conditions allowing expression of the antibody capable of        binding to CD3, and purifying the antibody capable of binding to        CD3 from the culture medium;    -   c) incubating said antibody capable of binding to 5T4 together        with said antibody capable of binding to CD3 under reducing        conditions sufficient to allow cysteines in the hinge region to        undergo disulfide-bond isomerization, and    -   d) obtaining said antibody.        Kits

The invention further provides a kit-of-parts comprising an antibody asdisclosed above, such as a kit for use as a companion diagnostic/foridentifying within a population of patients, those patients which have apropensity to respond to treatment with an antibody as defined hereinabove or an immunoconjugate or antibody-drug conjugate (ADC) as definedherein above, or for predicting efficacy or anti-tumor activity of saidantibody or immunoconjugate or ADC when used in treatment of a patient,the kit comprising an antibody as defined above; and instructions foruse of said kit.

Anti-Idiotypic Antibodies

In a further aspect, the invention relates to an anti-idiotypic antibodywhich binds to an antibody comprising at least one antigen-bindingregion capable of binding to 5T4, i.e. an antibody according to theinvention as described herein. In particular embodiments, theanti-idiotypic antibody binds to the antigen-binding region capable ofbinding to 5T4.

An anti-idiotypic (Id) antibody is an antibody which recognizes uniquedeterminants generally associated with the antigen-binding site of anantibody. An anti-Id antibody may be prepared by immunizing an animal ofthe same species and genetic type as the source of an anti-5T4monoclonal antibody with the monoclonal antibody against which ananti-Id is being prepared. The immunized animal typically can recognizeand respond to the idiotypic determinants of the immunizing antibody byproducing an antibody to these idiotypic determinants (the anti-Idantibody). Such antibodies are described in for instance U.S. Pat. No.4,699,880. Such antibodies are further features of the presentinvention.

An anti-Id antibody may also be used as an “immunogen” to induce animmune response in yet another animal, producing a so-calledanti-anti-Id antibody. An anti-anti-Id antibody may be epitopicallyidentical to the original monoclonal antibody, which induced the anti-Idantibody. Thus, by using antibodies to the idiotypic determinants of amonoclonal antibody, it is possible to identify other clones expressingantibodies of identical specificity. Anti-Id antibodies may be varied(thereby producing anti-Id antibody variants) and/or derivatized by anysuitable technique, such as those described elsewhere herein withrespect to 5T4-specific antibodies of the present invention. Forexample, a monoclonal anti-Id antibody may be coupled to a carrier suchas keyhole limpet hemocyanin (KLH) and used to immunize BALB/c mice.Sera from these mice typically will contain anti-anti-Id antibodies thathave the binding properties similar, if not identical, to anoriginal/parental anti-5T4 antibody.

Sequences SEQ ID NO: Name Domain Sequence 1 Human 5T4 ORFMPGGCSRGPAAGDGRLRLARLALVLLGWVSSSSPTSSASSFSSSAPFLASAVSAQPPLPDQCPALCECSEAARTVKCVNRNLTEVPTDLPAYVRNLFLTGNQLAVLPAGAFARRPPLAELAALNLSGSRLDEVRAGAFEHLPSLRQLDLSHNPLADLSPFAFSGSNASVSAPSPLVELILNHIVPPEDERQNRSFEGMVVAALLAGRALQGLRRLELASNHFLYLPRDVLAQLPSLRHLDLSNNSLVSLTYVSFRNLTHLESLHLEDNALKVLHNGTLAELQGLPHIRVFLDNNPWVCDCHMADMVTWLKETEVVQGKDRLTCAYPEKMRNRVLLELNSADLDCDPILPPSLQTSYVFLGIVLALIGAIFLLVLYLNRKGIKKWMHNIRDACRDHMEGYHYRYEINA DPRLTNLSSNSDV 2 Cynomolgus ORFMPGGCSRGPAAGDGRLRLARLALVLLGWVSSSSSTSSA monkey 5T4SSSSSSAPFLASAASAQPPLPDQCPALCECSEAARTVKCVNRNLTEVPTDLPLYVRNLFLTGNQLAVLPAGAFARRPPLAELAALNLSGSRLDEVRGGAFEHLPSLRQLDLSHNPLAYLSPFAFSGSNASISAPSPLVELILNHIVPPDDKRQNRSFEGMVAAALVAGRALQGLHLLELASNHFLYLPRDVLAQLPSLRYLDLSNNSLVSLTYVSFRNLTHLESLHLEDNALKVLHNGTLAELQGLPHVRVFLDNNPWVCDCHMADMVTWLKQTGVVQGKDRLTCAFPEKMRNRVLLELNSADLDCDPILPPSLQTSYVFLGIVLALIGAIFLLVLYLNRKGIKKWMHNIRDACRDHMEGYHYRYEINADPRLTNLSSNS DV 3 Chicken 5T4 ORFMPGREAERRGALCLGLLLHALLGCGSAQPPAACPAPCECSEAAKTVKCVNKNLTEVPPDLPPYVRNLFITGNRLGRLPAGALSAPRLAELGSLNLSGNHLRAVEAGALAALPALRQLDLGGNPLAELSPLAFGRASPLEELALRGALREQGALLGLADLLQAGALRNLSRLELADNGLLLLPTGMLGALPALRHLDLSNNSLVGLRNVSFQGLVRLQSLNLSDNSLGVLRNGTLAQWRGLPALRRISLSHNTWVCDCAIEDMVAWLKESDQVEGKEALSCAFPEKMAGRALLKLNTSELNCSAPVDVPSQLQTSYVFLGIVLALIGAIFLLVLYLNRKGIKKWMHNIRDACRDHMEGYHYRYEINADPRLTNLSSNSDV 4 Mature Human MatureQDGNEEMGGITQTPYKVSISGTTVILTCPQYPGSEILW CD3ε (epsilon) proteinQHNDKNIGGDEDDKNIGSDEDHLSLKEFSELEQSGYYVCYPRGSKPEDANFYLYLRARVCENCMEMDVMSVATIVIVDICITGGLLLLVYYWSKNRKAKAKPVTRGAGAGGRQRGQNKERPPPVPNPDYEPIRKGQRDLYSGLNQRRI 5 HC_5T4-059 VHQVQLVESGGGVVQPGRSLRLSCAVSGFTFSSYDMNWVRQAPGKGLEWVTFISYDGSNKYNADSVKGRFTISRDNSKNTLYLQMNSLRAEDTAVYYCARDSYSRSWYGDYYG MDVWGQGTTVTVSS 6 HC_5T4-059VH_CDR1 GFTFSSYD 7 HC_5T4-059 VH_CDR2 ISYDGSNK 8 HC_5T4-059 VH_CD_R3ARDSYSRSWYGDYYGMDV 9 LC_5T4-059 VLDIQMTQSPSSLSASVGDRVTITCRASQGISSWLAWYQQKPEKAPKSLIYAASSLQSGVPSRFSGSGSGTDFTLTISSL QPEDFATYYCQQYNSYPLTFGGGTKVEIK 10LC_5T4-059 VL_CDR1 QGISSW LC_5T4-059 VL_CDR2 AAS 11 LC_5T4-059 VL_CDR3QQYNSYPLT 12 HC_5T4-076 VH QVQLVQSGAEVKKPGASVKVSCKASGYTFTSYGISWVRQAPGQGLEWMGWISAYNGNTNYAQKLQGRVTMTTDTSTRTAYMELRSLRSDDTAVYYCARDPGYFDWLYGDYWGQG TLVTVSS 13 HC_5T4-076 VH_CDR1GYTFTSYG 14 HC_5T4-076 VH_CDR2 ISAYNGNT 15 HC_5T4-076 VH_CDR3ARDPGYFDWLYGDY 16 LC_5T4-076 VL AIQLTQSPSSLSASVGDRVTITCRASQGISSALAWYQQKPGKAPKLLIYDASSLESGVPSRFSGSGSGTDFTLTISSL QPEDFATYYCQQFNSYPRTFGQGTKVEIK 17LC_5T4-076 VL_CDR1 QGISSA LC_5T4-076 VL_CDR2 DAS 18 LC_5T4-076 VL_CDR3QQFNSYPRT 19 HC_5T4-085 VH EVQLLESGGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVSAISGSGGSTYNADSVKGRFTIFRDNSKNTLYLHMNSLRAEDTAVYYCARDPGYNNVEYLDHWGQG TLVTVSS 20 HC_5T4-085 VH_CDR1GFTFSSYA 21 HC_5T4-085 VH_CDR2 ISGSGGST 22 HC_5T4-085 VH_CDR3ARDPGYNNVEYLDH 23 LC_5T4-085 VL AIQLTQSPSSLSASVGDRVTITCRASQGISSALAWYQQKPGKAPKLLIYDASSLESGVPSRFSGSGSGTDFTLTISSL QPEDFATYYCQQFNSYPLTFGGGTKVEIK 24LC_5T4-085 VL_CDR1 QGISSA LC_5T4-085 VL_CDR2 DAS 25 LC_5T4-085 VL_CDR3QQFNSYPLT 26 HC_5T4-106 VH EVQLVQSGAEVKKPGESLKISCKGSGYRFTSYWIGWVRQMPGKGLEWMGIIYPGDSDARYSPSFQGQVTISADKSISTAYLQWSSLKASDTGMYYCARSVLFDYWGQGTLVTVS S 27 HC_5T4-106 VH_CDR1 GYRFTSYW28 HC_5T4-106 VH_CDR2 IYPGDSDA 29 HC_5T4-106 VH_CDR3 ARSVLFDY 30LC_5T4-106 VL AIQLTQSPSSLSASVGDRVTITCRASQGISSALAWYQQKPGKAPKLLIYDVSNLESGVPSRFSGSGSGTDFTLTISSL QPEDFATYYCQQFNSYPHTFGQGTKLEIK 31LC_5T4-106 VL_CDR1 QGISSA LC_5T4-106 VL_CDR2 DVS 32 LC_5T4-106 VL_CDR3QQFNSYPHT 33 HC_5T4-127 VH EVQLLESRGGLVQPGGSLRLSCAASGFTFSSYAMSWVRQAPGKGLEWVSTISGSGGSTYYADSVKGRFTISRDNSKKTLYLQMNSLRAEDTAVYYCAKDWGSGSYPAEYFQHWG QGTLVTVSS 34 HC_5T4-127 VH_CDR1GFTFSSYA 35 HC_5T4-127 VH_CDR2 ISGSGGST 36 HC_5T4-127 VH_CDR3AKDWGSGSYPAEYFQH 37 LC_5T4-127 VLEIVLTQSPATLSLSPGERATLSCRASQSVSSYLAWYQQKPGQAPRLLIYDASNRATGIPARFSGSGSGTDFTLTISSL EPEDFAVYYCQQRSNWLMYTFGQGTKLEIK38 LC_5T4-127 VL_CDR1 QSVSSY LC_5T4-127 VL_CDR2 DAS 39 LC_5T4-127VL_CDR3 QQRSNWLMYT 40 HC_5T4-207 VHQVQLQQWGAGLLKPSETLSLTCAVYGGSFSGYYWTWIRQPPGKGLEWIGEIDHSESTNYNPSLKSRVTISVDTSKNQFSLKLSSVTAADTAVYYCAGWFGELYHYYYGMDVWGQGTT VTVSS 41 HC_5T4-207 VH_CDR1GGSFSGYY 42 HC_5T4-207 VH_CDR2 IDHSEST 43 HC_5T4-207 VH_CDR3AGWFGELYHYYYGMDV 44 LC_5T4-207 VLEIVLTQSPATLSLSPGERATLSCRASQSVSSYLAWYQQKPGQAPRLLIYDASNRATGIPARFSGSGSGTDFTLTISSL EPEDFAVYYCQQRSNWPLTFGGGTKVEIK 45LC_5T4-207 VL_CDR1 QSVSSY LC_5T4-207 VL_CDR2 DAS 46 LC_5T4-207 VL_CDR3QQRSNWPLT 47 HC_5T4-226 VH QVQLQQWGAGLLKPSETLSLTCAVYGGSFSGYYWSWIRQPPGKGLEWIGEIDHSGSTNYNPSLKSRVTISVDTSKNQFSLKLSSVTAADTAVYYCAAWFGELWDYYYGMDV WGQGTTVTVSS 48 HC_5T4-226 VH_CDR1GGSFSGYY 49 HC_5T4-226 VH_CDR2 IDHSGST 50 HC_5T4-226 VH_CDR3AAWFGELWDYYYGMDV 51 LC_5T4-226 VLEIVLTQSPATLSLSPGERATLSCRASQSVSSFLAWYQQKPGQAPRLLIYDASNRATGIPARFSGSGSGTDFTLTISSL EPEDFAVYYCQQRSNWPLTFGQGTRLEIK 52LC_5T4-226 VL_CDR1 QSVSSF LC_5T4-226 VL_CDR2 DAS 53 LC_5T4-226 VL_CDR3QQRSNWPLT 54 VH_huCD3- VH_CDR1 GFTFNTYA H1L1_CDR1 55 VH_huCD3- VH_CDR2IRSKYNNYAT H1L1_CDR2 56 VH_huCD3- VH_CDR3 VRHGNFGNSYVSWFAY H1L1_CDR3 57VH_huCD3-H1L1 VH EVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISRDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FAYWGQGTLVTVSS 58 VL_huCD3-VL_CDR1 TGAVTTSNY H1L1_CDR1 VL_huCD3- VL_CDR2 GTN H1L1_CDR2 59 VL_huCD3-VL_CDR3 ALWYSNLWV H1L1_CDR3 60 VL_huCD3-H1L1 VLQAVVTQEPSFSVSPGGTVTLTCRSSTGAVTTSNYANWVQQTPGQAFRGLIGGTNKRAPGVPARFSGSLIGDKAALTITGAQADDESIYFCALWYSNLWVFGGGTKLTVL 61 VH CDR1-T31P VH_CDR1 GFTFNPYAHC_T31P CDR1 62 VH T31P full VH EVKLVESGGGLVQPGGSLRLSCAASGFTFNPYAMNWVlength sequence RQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_T31PDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FAYWGQGTLVTVSS 63 VH CDR1-T31MVH_CDR1 GFTFNMYA HC_T31M CDR1 64 VH T31M full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNMYAMNW length sequenceVRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTI HC_T31MSRDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSY VSWFAYWGQGTLVTVSS 65 VH CDR2-N57EVH_CDR2 IRSKYNEYAT HC_N57E CDR2 66 VH N57E full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNEYATYYADSVKDRFTISR HC_N57EDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FAYWGQGTLVTVSS 67 VH_huCD3-VH_CDR3 VRGGNFGNSYVSWFAY H1L1- H101G_CDR3 HC_H101G CDR3 68 VH_huCD3- VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV H1L1-H101GRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_H101GDDSKSSLYLQMNNLKTEDTAMYYCVRGGNFGNSYVSW FAYWGQGTLVTVSS 69 VH CDR3-H101NVH_CDR3 VRNGNFGNSYVSWFAY HC_H101N CDR3 70 VH H101N full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_H101NDDSKSSLYLQMNNLKTEDTAMYYCVRNGNFGNSYVSW FAYWGQGTLVTVSS 71 VH CDR3-G105PVH_CDR3 VRHGNFPNSYVSWFAY HC_G105P CDR3 72 VH G105P full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_G105PDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFPNSYVSW FAYWGQGTLVTVSS 73 VH CDR3-S110AVH_CDR3 VRHGNFGNSYVAWFAY HC_S110A CDR3 74 VH S110A full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_S110ADDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVAW FAYWGQGTLVTVSS 75 VH CDR3-S110GVH_CDR3 VRHGNFGNSYVGWFAY HC_S110G CDR3 76 VH S110G full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_S110GDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVGW FAYWGQGTLVTVSS 77 VH CDR3-Y114VVH_CDR3 VRHGNFGNSYVSWFAV HC_Y114V CDR3 78 VH Y114V full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_Y114VDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FAYWGQGTLVTVSS 79 VH CDR3-Y114MVH_CDR3 VRHGNFGNSYVSWFAM HC_Y114M CDR3 80 VH Y114M full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_Y114MDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FAMWGQGTLVTVSS 81 VH CDR3-Y114RVH_CDR3 VRHGNFGNSYVSWFAR HC_Y114R CDR3 82 VH Y114R full VHEVKLVESGGGLVQPGGSLRLSCAASGFTFNTYAMNWV length sequenceRQAPGKGLEWVARIRSKYNNYATYYADSVKDRFTISR HC_Y114RDDSKSSLYLQMNNLKTEDTAMYYCVRHGNFGNSYVSW FARWGQGTLVTVSS 83 HC_5T4-A1 VHQIQLVQSGPELKKPGETVKISCKASGYTFTNFGMNWVKQGPGEGLKWMGWINTNTGEPRYAEEFKGRFAFSLETTASTAYLQINNLKNEDTATYFCARDWDGAYFFDYWGQGTT LTVSS 84 LC_5T4-A1 VLSIVMTQTPKFLLVSAGDRVTITCKASQSVSNDVAWYQQKPGQSPKLLINFATNRYTGVPNRFTGSGYGTDFTFT ISTVQAEDLALYFCQQDYSSPWTFGGGTKLEIK85 HC_5T4-A3 VH EVQLVESGGGLVQPKGSLKLSCAASGFTFNTYAMNWVRQAPGKGLEWVARIRSKSNNYATYYADSVKDRFTISRDDSQSMLYLQMNNLKTEDTAMYYCVRQWDYDVRAM NYWGQGTSVTVSS 86 LC_5T4-A3 VLDIVMTQSHIFMSTSVGDRVSITCKASQDVDTAVAWYQQKPGQSPKLLIYWASTRLTGVPDRFTGSGSGTDFTLT ISNVQSEDLADYFCQQYSSYPYTFGGGTKLEIK87 HC_5T4-H8 VH EVQLQQSGPDLVKPGASVKISCKASGYSFTGYYMHWVKQSHGKSLEWIGRINPNNGVTLYNQKFKDKAILTVDSSTTAYMELRSLTSEDSAVYYCARSTMITNYVMDYWGQ VTSVTVSS 88 LC_5T4-H8 VLSIVMTQTPTFLLVSAGDRVTITCKASQSVSNDVAWYQQKPGQSPTLLISYTSSRYAGVPDRFIGSGYGTDFTFT ISTLQAEDLAVYFCQQDYNSPPTFGGGTKLEIK89 IgG1-Fc Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 90IgG1-Fc_F405L Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFLLYSKLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 91IgG1-Fc_FEA Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEFEGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSKLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 92IgG1-Fc_FEAL Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEFEGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFLLYSKLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 93IgG1-Fc_FEAR Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPEFEGGPSVFLFPPKPKDTLMISRTPEVTCVVVAVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 94IgG1-Fc_K409R Constant ASTKGPSVFPLAPSSKSTSGGTAALGCLVKDYFPEPVTVSWNSGALTSGVHTFPAVLQSSGLYSLSSVVTVPSSSLGTQTYICNVNHKPSNTKVDKRVEPKSCDKTHTCPPCPAPELLGGPSVFLFPPKPKDTLMISRTPEVTCVVVDVSHEDPEVKFNWYVDGVEVHNAKTKPREEQYNSTYRVVSVLTVLHQDWLNGKEYKCKVSNKALPAPIEKTISKAKGQPREPQVYTLPPSREEMTKNQVSLTCLVKGFYPSDIAVEWESNGQPENNYKTTPPVLDSDGSFFLYSRLTVDKSRWQQGNVFSCSVMH EALHNHYTQKSLSLSPGK 95 KappaConstant RTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSK ADYEKHKVYACEVTHQGLSSPVTKSFNRGEC96 Lambda Constant GQPKAAPSVTLFPPSSEELQANKATLVCLISDFYPGAVTVAWKADSSPVKAGVETTTPSKQSNNKYAASSYLSLTP EQWKSHRSYSCQVTHEGSTVEKTVAPTECS 97b12_VH VH QVQLVQSGAEVKKPGASVKVSCQASGYRFSNFVIHWVRQAPGQRFEWMGWINPYNGNKEFSAKFQDRVTFTADTSAMTAYMELRSLRSADTAVYYCARVGPYSWDDSPQDN YYMDVWGKGTTVIVSS 98 b12_VL VLEIVLTQSPGTLSLSPGERATFSCRSSHSIRSRRVAWYQHKPGQAPRLVIHGVSNRASGISDRFSGSGSGTDFTL TITRVEPEDFALYYCQVYGASSYTFGQGTKLERK99 5T4ECDHis ORF MPGGCSRGPAAGDGRLRLARLALVLLGWVSSSSPTSSASSFSSSAPFLASAVSAQPPLPDQCPALCECSEAARTVKCVNRNLTEVPTDLPAYVRNLFLTGNQLAVLPAGAFARRPPLAELAALNLSGSRLDEVRAGAFEHLPSLQLDLSHNPLADLSPFAFSGSNASVSAPSPLVELILNHIVPPEDERQNRSFEGMVVAALLAGRALQGLRRLELASNHFLYLPRDVLAQLPSLRHLDLSNNSLVSLTYVSFRNLTHLESLHLEDNALKVLHNGTLAELQGLPHIRVFLDNNPWVCDCHMADMVTWLKETEVVQGKDRLTCAYPEKMRNRVLLELNSADLD CDPILPPSLQTSHHHHHHHH 1005T4ECD91- ORF MPGGCSRGPAAGDGRLRLARLALVLLGWVSSSSPTSSAS FcRbHisSFSSSAPFLASAVSAQPPLPDQCPALCECSEAARTVKCVNRNLTEVPTDLPAAPSTCSKPTCPPPELLGGPSVFIFPPKPKDTLMISRTPEVTCVVVDVSQDDPEVQFTWYINNEQVRTARPPLREQQFNSTIRVVSTLPIAHQDWLRGKEFKCKVHNKALPAPIEKTISKARGQPLEPKVYTMGPPREELSSRSVSLTCMINGFYPSDISVEWEKNGKAEDNYKTTPAVLDSDGSYFLYSKLSVPTSEWQRGDVFTCSVMHEALTHNHYTQK SISRSPGKHHHHHHHH 101 CD3E27-GSKaORF MWWRLWWLLLLLLLLWPMVWAQDGNEEMGGITQTPYKVSISGTTVILTGGGGSGGGGSGGGGSEIVLTQSPATLSLSPGERATLSCRASQSVSSYLAWYQQKPGQAPRLLIYDASNRATGIPARFSGSGSGTDFTLTISSLEPEDFAVYYCQQRSNWPITFGQGTRLEIKRTVAAPSVFIFPPSDEQLKSGTASVVCLLNNFYPREAKVQWKVDNALQSGNSQESVTEQDSKDSTYSLSSTLTLSKADYEKHKVYACEVTHQGLSSPVTKSFN RGE 102 HC_574-059 VH-CDR3YYGMDV HC_5T4-207 C-term HC_5T4-226 103 HC_5T4-207 VH-CDR-2IDHSX₁ST; X₁ is G or E HC_5T4-226 104 HC_5T4-207 VH-CDR-3AX₂WFGELX₃X₄YYYGMDV; X₂ is A or G, HC_5T4-226 X₃ is W or Y, X₄ is D or H105 HC_5T4-207 VL-CDR-1 QSVSSX₅; X₅ is Y or F HC_5T4-226

The present invention is further illustrated by the following exampleswhich should not be construed as further limiting.

EXAMPLES Example 1—Generation of 5T4 Antibodies and Screenings Materials

Expression Constructs for 5T4 The following codon-optimized constructsfor expression of various full length 5T4 variants were generated: human(Homo sapiens) 5T4 (Uniprot accession no. Q13641), cynomolgus monkey(Macaca fascicularis) 5T4 (Uniprot accession no. Q4R8Y9), and chicken(Gallus gallus) 5T4 (Uniprot accession no. R4GM46). In addition, thefollowing codon-optimized constructs for various 5T4 extracellulardomain (ECD) variants were generated: the ECD of human 5T4 (aa 1-355from Uniprot accession no. Q13641) with a C-terminal His tag(5T4ECDHis)(SEQ ID NO: 99), and the ECD of human 5T4 (aa 1-91) fused torabbit Fc domain and C-terminal His-tag (5T4ECD91-FcRbHis). In SEQ IDNO: 99, amino acid residues 1-31 are a signal peptide; hence the mature5T4ECDHis protein corresponds to amino acid residues 32-363 of SEQ IDNO: 99. Likewise, amino acid residues 1-31 of SEQ ID NO: 100 are asignal peptide and the mature 5T4ECD91-FcRbHis protein corresponds toamino acid residues 32-327 of SEQ ID NO: 100.

The constructs contained suitable restriction sites for cloning and anoptimal Kozak (GCCGCCACC) sequence (Kozak, M., Gene 1999;234(2):187-208). The full length human 5T4 and cynomolgus monkey 5T4codon-optimized constructs were cloned in the mammalian expressionvector pcDNA3.3 (Invitrogen). The full length chicken 5T4codon-optimized constructs was cloned in pSB, a mammalian expressionvector containing Sleeping Beauty inverter terminal repeats flanking anexpression cassette consisting of a CMV promoter and HSV-TK polyAsignal.

Generation of HEK-293F cell lines transiently expressing full lengthhuman, cynomolgus or chicken 5T4 Freestyle™ 293-F (a HEK-293 subcloneadapted to suspension growth and chemically defined Freestyle medium[HEK-293F]) cells were obtained from Invitrogen (cat. no. R790-07) andtransfected with the codon-optimized constructs described supra, using293fectin (Invitrogen, cat. no. 12347-019) according to themanufacturer's instructions.

Purification of His-Tagged 5T4

5T4ECDHis (mature protein of SEQ ID NO: 99) was expressed in HEK-293Fcells as described supra. 5T4ECD91-FcRbHis was expressed using theExpi293F expression platform (Thermo Fisher Scientific, Waltham, Mass.,USA, cat. no. A14527) essentially as described by the manufacturer.

The His-tag enables purification with immobilized metal affinitychromatography. In this process, a chelator fixed onto thechromatographic resin is charged with Co²⁺ cations. Supernatantscontaining the His-tagged protein were incubated with the resin in batchmode (i.e. solution). The His-tagged protein binds strongly to the resinbeads, while other proteins present in the culture supernatant do notbind or bind weakly compared to the His-tagged proteins. Afterincubation, the beads were retrieved from the supernatant and packedinto a column. The column was washed in order to remove weakly boundproteins. The strongly bound His-tagged proteins were then eluted with abuffer containing imidazole, which competes with the binding of His toCo²⁺. The eluent was removed by buffer exchange on a desalting column.

Immunization

For generation of antibodies IgG1-5T4-207 and IgG1-5T4-226, HCo17-BalbCtransgenic mice (Bristol-Myers Squibb, New York, N.Y., USA) wereimmunized alternatingly intraperitoneally (IP) and subcutaneously (SC)with 20 μg of the 5T4ECDHis protein in Sigma adjuvant system(Sigma-Aldrich, St. Louis, Mo., USA, cat. no. S6322) with an interval of14 days. In total 8 immunizations were performed: 4 IP and 4 SC.

For generation of antibodies IgG1-5T4-076 and IgG1-5T4-059, HCo12-BalbC(IgG1-5T4-076) and HCo20-BalbC (IgG1-5T4-059) transgenic mice(Bristol-Myers Squibb) were immunized alternatingly IP and SC with 20 μgof the 5T4ECDHis protein in Sigma adjuvant system with an interval of 14days. In total 8 immunizations were performed: 4 IP and 4 SC.

For generation of antibody IgG1-5T4-085, HCo17-BalbC transgenic micewere immunized alternatingly IP and SC with 20 μg of the 5T4ECDHisprotein and 20 μg of the 5T4ECD91-FcRbHis mature protein in Sigmaadjuvant system with an interval of 14 days. In total 8 immunizationswere performed: 4 IP and 4 SC.

For generation of antibodies IgG1-5T4-106 and IgG1-5T4-127, HCo12-BalbC(IgG1-5T4-106) and HCo17-BalbC (IgG1-5T4-127) transgenic mice wereimmunized alternatingly IP and SC with 20 μg of the 5T4ECD91-FcRbHismature protein in Sigma adjuvant system with an interval of 14 days. Intotal 8 immunizations were performed: 4 IP and 4 SC.

Mice with at least two sequential 5T4 specific antibody titers in theantigen specific screening Fluorometric Micro volume Assay Technology(FMAT) as described below, were boosted with 10 μg of 5T4ECDHis or 10 μg5T4ECD91-FcRbHis (in PBS injected intravenously) and splenocytes andlymph node cells of these mice were fused 3-4 days later.

Homogeneous Antigen Specific Screening Assay

The presence of 5T4 antibodies in sera of immunized mice or HuMAb (humanmonoclonal antibody) hybridoma or transfectoma culture supernatant wasdetermined by homogeneous antigen specific screening assays using FMAT(Applied Biosystems, Foster City, Calif., USA). For this, a combinationof 4 cell based assays was used.

Sera from immunized mice, or hybridoma or transfectoma culturesupernatant samples were analyzed for binding of human antibodies toHEK-293F cells transiently expressing human 5T4, HEK-293F cellstransiently expressing cynomolgus monkey 5T4, streptavidin-coatedpolystyrene particles (0.5% w/v; 6.7 μm; Spherotech, Lake Forest, Ill.,USA, cat. no. SVP-60-5) coated with 5T4ECD91-FcRBHis, and HEK-293wild-type cells (negative control).

Samples were added to the cells to allow binding to 5T4. Subsequently,binding of HuMAb was detected using a fluorescent conjugate (AffiniPureGoat Anti-Human IgG Fc gamma-Alexa Fluor® 647; Jackson ImmunoResearch,cat no. 109-605-098). IgG1-5T4-H8-F405L was used as a positive controland ChromPure Human IgG, whole molecule (Jackson ImmunoResearch, cat no.009-000-003) was used as negative control. The samples were scannedusing an ImageXpress Velos (Molecular devices, LLC, Sunnyvale, Calif.,USA) and total fluorescence was used as read-out. Samples were statedpositive when counts were higher than 50 and counts×fluorescence was atleast three times higher than the negative control.

HuMAb Hybridoma Generation

HuMAb mice with sufficient antigen-specific titer development (describedabove) were sacrificed and the spleen and lymph nodes flanking theabdominal aorta and vena cava were collected. Fusion of splenocytes andlymph node cells to a mouse myeloma cell line (SP2.0 cells) was done byelectrofusion using a CytoPulse CEEF 50 Electrofusion System (Cellectis,Paris, France), essentially according to the manufacturer'sinstructions. Next, the antigen-positive primary wells were sub-clonedusing the ClonePix system (Genetix, Hampshire, UK). To this end,specific primary well hybridomas were seeded in semisolid medium madefrom 40% CloneMedia (Genetix, Hampshire, UK) and 60% HyQ 2× completemedia (Hyclone, Waltham, USA). The subclones were retested for 5T4binding according to the antigen-specific binding assay as describedabove and scanned using the IsoCyte system (Molecular Devices). IgGlevels were measured using an Octet system (Fortebio, Menlo Park, USA)in order to select the best producing clone per primary well for furtherexpansion. Further expansion and culturing of the resulting HuMAbhybridomas were done based upon standard protocols (e.g. as described inColigan J. E., Bierer, B. E., Margulies, D. H., Shevach, E. M. andStrober, W., eds. Current Protocols in Immunology, John Wiley & Sons,Inc., 2006).

Sequence Analysis of the 5T4 Antibody Variable Domains and Cloning inExpression Vectors

Total RNA was prepared from 2 to 5×10⁶ hybridoma cells and5′-RACE-complementary DNA (cDNA) was prepared from 100 ng total RNA,using the SMART RACE cDNA Amplification kit (Clontech), according to themanufacturer's instructions. VH and VL coding regions were amplified byPCR and cloned directly, in frame, in the p33G1f and p33Kappa expressionvectors (pcDNA3.3 based vectors with codon optimized human IgG1m(f) andKappa constant domains, respectively), by ligation independent cloning(Aslanidis, C. and P. J. de Jong, Nucleic Acids Res 1990; 18(20):6069-74). The variable domains from these expression vectors weresequenced and CDRs were annotated according to IMGT definitions (LefrancM P. et al., Nucleic Acids Research, 27, 209-212, 1999 and Brochet X.Nucl. Acids Res. 36, W503-508 (2008)). Clones with a correct OpenReading Frame (ORF) were expressed and tested for binding to theantigen. A lead panel was ordered as codon optimized sequences (GeneArt,Thermo Fisher Scientific) and produced with the Expi293 expressionsystem according to manufacturer's instructions (Thermo FisherScientific). The antibodies in these supernatants were purified and usedfor functional characterization. The sequences of the resulting leadclones are shown in the table above.

5T4 Control Antibodies

In some of the Examples comparison antibodies against 5T4 were used(IgG1-5T4-H8, IgG1-5T4-A3 and IgG1-5T4-A1) that have been previouslydescribed in WO2007/106744. The codon optimized antibody encodingsequences were synthesized and cloned in pCDNA3.3 expression vectors(Thermo Fisher Scientific).

IgG1-b12 Antibody

In some of the Examples the antibody b12, an HIV-1 gp120 specificantibody (Barbas, C F. J Mol Biol. 1993 Apr. 5; 230(3):812-23) was usedas a negative control. The codon optimized antibody encoding sequencesfor this control antibody were synthesized and cloned into pCDNA3.3expression vectors (Thermo Fisher Scientific). The sequence of thevariable heavy chain (VH) region and the sequence of the variable lightchain (VL) region are included herein as SEQ ID NOs.: 97 and 98,respectively.

Example 2—Determination of the Binding Affinities of 5T4 SpecificAntibodies Using Biolayer Interferometry

Affinities of the 5T4 antibodies for recombinant 5T4 protein weredetermined using label-free biolayer interferometry on an Octet HTXinstrument (ForteBio, Portsmouth, UK). 5T4 antibodies (1 μg/mL) wereimmobilized for 600 seconds on anti-human IgG Fc Capture biosensors(ForteBio). After a baseline measurement (100 s), the association (200s) and dissociation (1000 s) of human 5T4ECDHis (mature protein of SEQID NO: 99) or recombinant cynomolgus monkey 5T4 protein (Cusabio; cat.no. CSB-MP024093MOV) in Sample Diluent (ForteBio) was determined using a2-fold dilution series (ranging from 100 nM to 1.56 nM) starting at 3.58μg/mL (100 nM) human 5T4ECDHis or 3.99 μg/mL (100 nM) cynomolgus 5T4,while shaking at 1000 rpm at 30° C. Data were analyzed with DataAnalysis Software v9.0.0.12 (ForteBio). Values of reference wellscontaining only Sample Diluent during the association and dissociationsteps were subtracted from values of wells containing antigen, for eachantibody separately. The Y-axis was aligned to the last 10 s of thebaseline and Interstep Correction alignment to dissociation as well asSavitzky-Golay filtering was applied. Responses <0.05 nm were excludedfrom analysis. The data were fitted using the 1:1 model and a globalfull fit with 200 s association time and 1000 s or 50 s dissociationtime as Window of Interest. The fit with the full dissociation time(1000 s) as Window of Interest was used by default. Based on the R²value and visual inspection of the fit, a dissociation time of 50s wasused as Window of Interest for IgG1-5T4-127-FEAR.

Table 1 shows the association rate constant k_(a) (1/Ms), dissociationrate constant k_(d) (1/s) and equilibrium dissociation constant K_(D)(M) of the 5T4 antibodies for human 5T4ECDHis determined by biolayerinterferometry. A range of affinities of the antibodies to human 5T4 wasmeasured ranging from 1.3×10⁻⁸-2.7×10⁻⁸ M. The response ofIgG1-5T4-085-FEAR was lower than 0.05 nm, which prevented proper fittingof the data (low R² values for these fits). Furthermore, the response ofIgG1-5T4-076-FEAR could not be fitted properly. These data are shown initalics.

Table 2 shows the association rate constant k_(a) (1/Ms), dissociationrate constant k_(d) (1/s) and equilibrium dissociation constant K_(D)(M) for cynomolgus monkey 5T4 determined with biolayer interferometry. Arange of affinities of the antibodies to cynomolgus monkey 5T4 wasmeasured ranging from 1.1×10⁻⁸-4.1×10⁻⁸ M. The responses ofIgG1-5T4-085-FEAR, IgG1-5T4-106-FEAR and IgG1-5T4-H8-FEAR were lowerthan 0.05 nm, which prevented proper fitting of the data (low R² valuesfor these fits). Furthermore, the response of IgG1-5T4-076-FEAR couldnot be fitted properly. These data are shown in italics.

TABLE 1 Binding affinities of monospecific, bivalent 5T4 antibodies tohuman 5T4 extracellular domain as determined by label-free biolayerinterferometry. On-rate Off-rate Antibody k_(a) (1/Ms) k_(d) (1/s) K_(D)(M) IgG1-5T4-059-FEAR 2.1E+05 3.2E−04 1.5E−09 IgG1-5T4-076-FEAR No fitIgG1-5T4-085-FEAR Response <0.05 nm IgG1-5T4-106-FEAR 2.1E+05 1.2E−035.5E−09 IgG1-5T4-127-FEAR 5.8E+05 1.6E−02 2.7E−08 IgG1-5T4-207-FEAR2.7E+05 6.8E−04 2.6E−09 IgG1-5T4-226-FEAR 3.3E+05 8.1E−04 2.5E−09IgG1-5T4-H8-FEAR 2.2E+05 2.9E−04 1.3E−09

TABLE 2 Binding affinities of monospecific, bivalent 5T4 antibodies tocynomolgus monkey 5T4 extracellular domain as determined by label-freebiolayer interferometry. On-rate Off-rate Antibody k_(a) (1/Ms) k_(d)(1/s) K_(D) (M) IgG1-5T4-059-FEAR 1.6E+05 2.8E−04 1.8E−09IgG1-5T4-076-FEAR No fit IgG1-5T4-085-FEAR Response <0.05 nmIgG1-5T4-106-FEAR Response <0.05 nm IgG1-5T4-127-FEAR 3.7E+05 1.5E−024.1E−08 IgG1-5T4-207-FEAR 1.4E+05 8.7E−04 6.3E−09 IgG1-5T4-226-FEAR1.4E+05 1.5E−03 1.1E−08 IgG1-5T4-H8-FEAR Response <0.05 nm

Example 3—Cross-Block of 5T4 Antibodies Determined by BiolayerInterferometry

Antibody cross-block analysis (epitope binning) was performed usingbiolayer interferometry on an Octet HTX instrument (ForteBio). 5T4antibodies (20 μg/mL in 10 mM sodium acetate buffer pH 6.0, ForteBio)were immobilized on Amine-Reactive 2nd Generation (AR2G) biosensors(ForteBio) according to the manufacturer's instructions. After abaseline measurement (100 s) in Sample Diluent (ForteBio), biosensorscontaining immobilized antibodies were loaded for 500 s with human5T4ECDHis (mature protein of SEQ ID NO: 99) 100 nM (3.6 μg/mL). Next,the association response of a second 5T4 antibody (10 μg/mL) wasdetermined for 500 s. Biosensors were regenerated by 3 times 5 sexposure to 10 mM glycine pH 2.5 followed by Sample Diluent, and themeasurement was repeated with a new set of second 5T4 antibodiesstarting from the baseline step. Each biosensor was used four times.Measurements were performed at 30° C. using a shaker speed of 1000 rpm.Data were analyzed using Data Analysis Software v9.0.0.12 (ForteBio).The Y-axis was aligned to the association step and Savitzky-Golayfiltering was applied. The response of Sample Diluent during theassociation step was subtracted from the association response of thesecond antibody in order to correct for the dissociation of 5T4ECDHisfrom the immobilized antibody. The corrected association responses wereplotted in a matrix format. In general, responses >0.1 nm wereconsidered non-blocking antibody pairs (white), while responses between−0.1 and 0.1 nm were considered to be blocking antibody pairs (darkgrey). For some antibody pairs the second antibody showed an initialpositive response, followed by a decrease in signal. This was consideredto be antibody displacement (light grey), i.e. the second antibodydisplacing the interaction between the first antibody and the antigen(Abdiche Y N, Yeung A Y, Ni I, Stone D, Miles A, Morishige W, et al.(2017) Antibodies Targeting Closely Adjacent or Minimally OverlappingEpitopes Can Displace One Another. PLoS ONE 12(1): e0169535.doi:10.1371/journal.pone.0169535). In some cases, the data curves neededvisual inspection by an expert to assign blocking, non-blocking ordisplacement properties to antibody pairs.

Cross-block experiments were performed for antibodies IgG1-5T4-059-FEAR,IgG1-5T4-076-FEAR, IgG1-5T4-085-FEAR, IgG1-5T4-106-FEAR,IgG1-5T4-127-FEAR, IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR, and prior artantibodies IgG1-5T4-H8-FEAR, IgG1-5T4-A1-F405L and IgG1-5T4-A3-F405L.The results are summarized in Table 3.

None of the antibodies (except IgG1-5T4-A1-F405L itself) blocked bindingof IgG1-5T4-A1-F405L to 5T4ECDHis. Antibodies IgG1-5T4-076-FEAR,IgG1-5T4-085-FEAR, IgG1-5T4-127-FEAR, IgG1-5T4-106-FEAR,IgG1-5T4-059-FEAR, IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR (as well asIgG1-5T4-H8-FEAR itself) blocked binding of IgG1-5T4-H8-FEAR to5T4ECDHis. Antibodies IgG1-5T4-076-FEAR, IgG1-5T4-085-FEAR, andIgG1-5T4-127-FEAR (as well as IgG1-5T4-A3-F405L itself) also blockedbinding of IgG1-5T4-A3-F405L to 5T4ECDHis, while antibodiesIgG1-5T4-106-FEAR and IgG1-5T4-H8-FEAR did not block binding ofIgG1-5T4-A3-F405L to 5T4ECDHis. Antibodies IgG1-5T4-059-FEAR,IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR showed antibody displacement incombination with IgG1-5T4-A3-F405L, which is described in more detail inExample 4.

Table 3: Antibody cross-block as determined by biolayer interferometry.

The first column shows the immobilized antibodies and the first rowshows the antibodies in solution. Corrected association responses of theantibodies in solution are shown. Cross-block of antibodies is indicatedby italics and underlining, displacing antibody combinations areindicated by an asterisk. Non-blocking antibody combinations areunmarked.

TABLE 3 Antibody cross-block as determined by biolayer interferometry.A1 A3 076 085 127 106 H8 059 207 226 A1 −0.01 0.76 0.36 0.72 0.87 0.850.89 0.91 0.86 0.86 A3 0.69 0.01 0.00 0.00 0.01 0.57 0.50 * * * 076 0.040.00 −0.01 −0.02 −0.02 −0.02 0.00 −0.02 0.05 0.05 085 0.07 −0.01 −0.01−0.01 0.00 −0.01 −0.01 −0.04 0.08 0.07 127 0.15 −0.01 −0.02 −0.01 −0.01−0.01 −0.02 −0.05 0.16 0.16 106 0.79 0.56 −0.03 −0.04 −0.02 −0.02 −0.02−0.03 −0.03 −0.02 H8 0.64 0.49 −0.02 −0.02 −0.01 −0.01 0.00 −0.02 −0.01−0.01 059 0.96 * 0.00 −0.02 −0.10 0.01 0.01 0.01 0.02 0.01 207 1.29 *1.22 1.03 1.29 −0.01 −0.01 −0.02 −0.02 −0.02 226 1.56 * 1.47 1.35 1.51−0.02 −0.01 −0.02 −0.02 −0.02

Example 4—Antibody Displacement of IgG1-5T4-059-FEAR, IgG1-5T4-207-FEARand IgG1-5T4-226-FEAR in Combination with IgG1-5T4-A3-F405L

Antibody displacement was demonstrated using biolayer interferometry onan Octet HTX instrument (ForteBio). IgG1-5T4-A3-F405L (20 μg/mL in 10 mMsodium acetate buffer pH 6.0, ForteBio) was immobilized onAmine-Reactive 2nd Generation (AR2G) biosensors (ForteBio) according tothe manufacturer's instructions. After a baseline measurement (100 s) inSample Diluent (ForteBio), biosensors containing immobilizedIgG1-5T4-A3-F405L antibodies were loaded for 500 s with human 5T4ECDHis(mature protein of SEQ ID NO: 99) 100 nM (3.6 μg/mL). Next, theassociation response of a second 5T4 antibody (IgG1-5T4-059-FEAR,IgG1-5T4-207-FEAR or IgG1-5T4-226-FEAR; 10 μg/mL) or Sample Diluent(buffer control) was determined for 500 s. The experiment was performedat 30° C. using a shaker speed of 1000 rpm. Data was analyzed using DataAnalysis Software v9.0.0.12 (ForteBio). The buffer control response wassubtracted from the responses of the second antibodies to correct forthe dissociation of human 5T4ECDHis from the immobilizedIgG1-5T4-A3-F405L, the Y-axis was aligned to the association step andSavitzky-Golay filtering was applied.

As shown in FIG. 1, IgG1-5T4-A3-F405L did not show binding, indicatingcross-block (self-block) with IgG1-5T4-A3-F405L. IgG1-5T4-H8-FEAR showedbinding to 5T4ECDHis and hence no cross-block with IgG1-5T4-A3-F405L.IgG1-5T4-059-FEAR, IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR initiallyshowed a positive response (indicating binding to theIgG1-5T4-A3-F405L-5T4ECDHis complex instead of cross-blocking withIgG1-5T4-A3-F405L), followed by a decrease in response that droppedbelow the self-block response of IgG1-5T4-A3-F405L. This demonstratesloss of mass from the IgG1-5T4-A3-F405L-5T4ECDHis complex, indicatingthat IgG1-5T4-059-FEAR, IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR inducedissociation of human 5T4ECDHis from IgG1-5T4-A3-F405L upon binding tothe complex. This phenomenon has been described as antibody displacementand indicates that the epitopes are closely adjacent or minimallyoverlapping (Abdiche Y N, Yeung A Y, Ni I, Stone D, Miles A, MorishigeW, et al. (2017) Antibodies Targeting Closely Adjacent or MinimallyOverlapping Epitopes Can Displace One Another. PLoS ONE 12(1): e0169535.doi:10.1371/journal.pone.0169535)). This indicates that antibodiesIgG1-5T4-059-FEAR, IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR bind to adistinct epitope on 5T4 as compared to IgG1-5T4-A3-F405L.

Example 5—Simultaneous Binding of 5T4 Antibodies to Membrane-Bound 5T4Measured with Flow Cytometry

Binding of IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR antibodies tomembrane-bound 5T4 in the presence of IgG1-5T4-A1-F405L andIgG1-5T4-A3-F405L was assessed by flow cytometry. IgG1-5T4-H8-FEAR,IgG1-5T4-207-FEAR and IgG1-5T4-226-FEAR were conjugated to fluoresceinisothiocyanate (FITC, Thermo Fisher Scientific) according tomanufacturer's instructions. SK-OV-3 cells (50,000 cells per condition),which express approximately 20,000 5T4 molecules/cell, were incubatedwith mixtures of 10 μg/mL unconjugated 5T4 antibodies (IgG1-5T4-H8-FEAR,IgG1-5T4-A1-F405L, IgG1-5T4-A3-F405L, IgG1-b12, IgG1-5T4-207-FEAR orIgG1-5T4-226-FEAR) and 2 μg/mL FITC-conjugated 5T4 antibodies(IgG1-5T4-H8-FEAR-FITC, IgG1-5T4-207-FEAR-FITC andIgG1-5T4-226-FEAR-FITC). Table 4 shows an overview of the testedcombinations. After 30 min incubation at 4° C., cells were centrifugedat 1200 RPM for 5 min, and the supernatant was discarded. The cells wereresuspended in 100 μL FACS-buffer supplemented with 1:4000Topro-3-iodine (Molecular Probes). Mean fluorescence intensity (MFI) ofthe FITC signal was measured using a flow cytometer (FACS Fortessa, BDBiosciences). Percentage of binding was calculated using the followingformula:([MFI of cells with Ab-FITC and unconjugated Ab−MEI of cells withoutAb-FITC or unconjugated Ab]*100)/(MEI of cells with Ab-FITC and isotypecontrol−MEI of cells without Ab-FITC or unconjugated Ab)

FIG. 2 shows that binding of IgG1-5T4-H8-FEAR-FITC,IgG1-5T4-207-FEAR-FITC and IgG1-5T4-226-FEAR-FITC was blocked inpresence of their unconjugated counterpart. However, binding ofIgG1-5T4-207-FEAR-FITC and IgG1-5T4-226-FEAR-FITC to membrane-bound 5T4was still observed in the presence of unconjugated IgG1-5T4-A1-F405L,IgG1-5T4-A3-F405L or IgG1-b12, and was comparable to binding ofIgG1-5T4-H8-FEAR-FITC to membrane-bound 5T4 in the presence ofunconjugated IgG1-5T4-A1-F405L, IgG1-5T4-A3-F405L or IgG1-b12. Thisdemonstrates that antibodies IgG1-5T4-H8-FEAR, IgG1-5T4-207-FEAR andIgG1-5T4-226-FEAR bind to a distinct epitope on 5T4 as compared toantibodies IgG1-5T4-A1-F405L and IgG1-5T4-A3-F405L.

TABLE 4 Overview of antibody combinations used in flow cytometryexperiment. FITC-labeled antibody (2 μg/mL) Unconjugated antibody (10μg/mL)  1 IgG1-5T4-H8-FEAR-FITC IgG1-5T4-H8-FEAR  2IgG1-5T4-H8-FEAR-FITC IgG1-5T4-A3-F405L  3 IgG1-5T4-H8-FEAR-FITCIgG1-5T4-207-FEAR  4 IgG1-5T4-H8-FEAR-FITC IgG1-5T4-226-FEAR  5IgG1-5T4-H8-FEAR-FITC IgG1-5T4-A1-F405L  6 IgG1-5T4-H8-FEAR-FITCIgG1-b12  7 IgG1-5T4-207-FEAR-FITC IgG1-5T4-H8-FEAR  8IgG1-5T4-207-FEAR-FITC IgG1-5T4-A3-F405L  9 IgG1-5T4-207-FEAR-FITCIgG1-5T4-207-FEAR 10 IgG1-5T4-207-FEAR-FITC IgG1-5T4-226-FEAR 11IgG1-5T4-207-FEAR-FITC IgG1-5T4-A1-F405L 12 IgG1-5T4-207-FEAR-FITCIgG1-b12 13 IgG1-5T4-226-FEAR-FITC IgG1-5T4-H8-FEAR 14IgG1-5T4-226-FEAR-FITC IgG1-5T4-A3-F405L 15 IgG1-5T4-226-FEAR-FITCIgG1-5T4-207-FEAR 16 IgG1-5T4-226-FEAR-FITC IgG1-5T4-226-FEAR 17IgG1-5T4-226-FEAR-FITC IgG1-5T4-A1-F405L 18 IgG1-5T4-226-FEAR-FITCIgG1-b12

Example 6—Binding of 5T4 Antibodies to HEK-293 Cells Transfected withHuman or Chicken 5T4

Binding of 5T4 antibodies to HEK-293 cells transiently transfected withfull length human or chicken 5T4 (generated as described in Example 1)was analyzed by flow cytometry. Cells (5×10⁴ cells/well) were incubatedin polystyrene 96-well round-bottom plates (Greiner bio-one, cat. no.650180) with serial dilutions of 5T4 antibodies (range 0.01 to 10 μg/mLin 3-fold dilution steps) in 50 μL PBS/0.1% BSA/0.02% azide (stainingbuffer) at 4° C. for 30 min. After washing twice in staining buffer,cells were incubated in 50 μL R-Phycoerythrin (PE)-conjugatedgoat-anti-human IgG F(ab′)₂ (1:500 in staining buffer; JacksonImmunoResearch Laboratories, Inc., West Grove, Pa., cat. no.109-116-098) at 4° C. for 30 min. Cells were washed twice in stainingbuffer, re-suspended in 20 μL staining buffer and analyzed on an iQuescreener (Intellicyt Corporation, USA). Binding curves were analyzed bynon-linear regression (sigmoidal dose-response with variable slope)using GraphPad Prism V7.02 software (GraphPad Software, San Diego,Calif., USA).

FIG. 3A shows dose-dependent binding of IgG1-5T4-207-FEAR,IgG1-5T4-226-FEAR, IgG1-5T4-059-FEAR and IgG1-5T4-A3-F405L to HEK-293cells transfected with full length human 5T4. FIG. 3B shows that whiledose-dependent binding of IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR andIgG1-5T4-059-FEAR to HEK-293 cells transfected with full length chicken5T4 was observed, IgG1-5T4-A3-F405L showed minimal binding to HEK-293cells transfected with full length chicken 5T4. The negative controlantibody, IgG1-b12-K409R, did not show binding to HEK-293 cellstransfected with full length human or chicken 5T4 at a concentration of10 μg/mL.

Example 7—Internalization Capacity of 5T4 Antibodies in Tumor Cells

Experiments were performed to characterize the internalization capacityof monovalent 5T4 antibodies. Intracellular payload delivery andresulting cytotoxicity were used as a read out for internalization ofthe 5T4 antibodies upon target binding. Bispecific, toxin-conjugatedantibodies that recognize 5T4 with one Fab-arm while recognizing anirrelevant antigen (HIV-1 gp120, which is not expressed on tumor cells)with the second Fab-arm, were generated by controlled Fab-arm exchangeof unconjugated 5T4 antibodies with (HIV-1 gp120-specific) IgG1-b12antibodies that had been conjugated with the microtubule-disruptingagent Duostatin-3. The resulting bispecific Duostatin-3 conjugatedantibodies carry 1 toxin molecule per antibody (drug-antibody ratio 1).Serial dilutions (0.00152-10 μg/mL, 3-fold) of Duostatin-3 conjugatedbispecific antibodies that monovalently bind 5T4, were added toMDA-MB-468 (mammary cancer cell line, ATCC, clone HTB-132) or HCC1954(mammary cancer cell line, ATCC, clone CRL-2338) cells seeded inflat-bottom 96-well tissue culture plates (5,000 cells/well;Greiner-bio-one, The Netherlands, cat. no. 655180). The cells wereincubated for 5 days at 37° C., after which cell viability was assessedusing a CellTiter-Glo Luminescent Cell Viability Assay (Promega, USA,cat. no. G7570) according to manufacturer's instructions. Cytotoxicitycurves were analyzed using non-linear regression (sigmoidaldose-response with variable slope) using GraphPad Prism V7.02 software(Graph Pad Software, San Diego, Calif., USA).

FIG. 4 shows the cytotoxic capacity of Duostatin-3 conjugated bispecificantibodies that monovalently bind 5T4 in MDA-MB-468 (A) or HCC1954 cells(B). BsIgG1-5T4-H8-FEARxb12-vcDuo3 was highly capable of inducingcytotoxicity, indicative of an effective internalization capacity of theantibody. In contrast, bsIgG1-5T4-076-FEARxb12-vcDuo3,bsIgG1-5T4-085-FEARxb12-vcDuo3 and bsIgG1-5T4-127-FEARxb12-vcDuo3 didnot induce any cytotoxicity; dose response curves were similar to thatof the non-binding IgG1-b12-vcDuo3 control antibody. This indicates poorinternalization of those antibodies upon binding to membrane-bound 5T4.BsIgG1-5T4-059-FEARxb12-vcDuo3, bsIgG1-5T4-106-FEARxb12-vcDuo3,bsIgG1-5T4-207-FEARxb12-vcDuo3, and bsIgG1-5T4-226-FEARxb12-vcDuo3induced intermediate cytotoxicity in both tested cell lines, indicatingthat these monovalent 5T4 antibodies induced internalization but to alesser extent than bsIgG1-5T4-H8-FEARxb12-vcDuo3.

Example 8—Humanized CD3 Antibodies for the Generation of CD3×5T4Bispecific Antibodies

The generation of humanized antibody IgG1-huCD3-H1L1 is described inExample 1 of WO2015/001085. IgG1-huCD3-H1L1 is referred to herein as‘IgG1-huCD3’. Antibody IgG1-huCD3-H1L1-FEAL is a variant hereof withamino acid substitutions in the Fc domain that prevent interactions withIgG Fc receptors (Fc gamma receptors [FcγR]) and complement, in additionto a mutation that allows the generation of bispecific antibodiesthrough controlled Fab-arm exchange: L234F, L235E, D265A and F405L, asdescribed herein above. It has previously been demonstrated that thesemutation have no effect on target binding of the antibodies in whichthey are introduced (see e.g. US 2015/0337049)

The generation of humanized antibody IgG1-huCD3-H1L1-H101G is describedin Example 2 of WO2017/009442. IgG1-huCD3-H1L1-H101G will be referred toas ‘IgG1-huCD3-H101G’. Antibody IgG1-huCD3-H101G-FEAL is a varianthereof with amino acid substitutions L234F, L235E, D265A and F405L, asdescribed herein above.

Example 9—CD3 Binding Affinity Determination Using BiolayerInterferometry

Binding affinities of selected CD3 antibodies, including IgG1-huCD3 andIgG1-huCD3-H101G, were determined as described in Example 7 ofWO2017/009442.

In short, binding affinities of selected CD3 antibodies in anIgG1-huCD3-FEAL format to for recombinant soluble CD3E (CD3E27-GSKa)(mature protein of SEQ ID NO: 101) were determined using biolayerinterferometry on a ForteBio Octet HTX (ForteBio). Anti-human Fc capturebiosensors (ForteBio, cat. no. 18-5060) were loaded for 600 s with hIgG(1 mg/mL). After a baseline measurement (200 s), the association (1000s) and dissociation (2000 s) of CD3E27-GSKa was determined, using aCD3E27-GSKa concentration range of 27.11 μg/mL-0.04 μg/mL (1000 nM-1.4nM) with three-fold dilution steps (sample diluent, ForteBio, cat. no.18-5028). For calculations, the theoretical molecular mass ofCD3E27-GSKa based on the amino acid sequence was used, i.e. 27.11 kDa.Experiments were carried out while shaking at 1000 rpm and at 30° C.Each antibody was tested in at least two independent experiments. Datawas analyzed with ForteBio Data Analysis Software v8.1, using the 1:1model and a global full fit with 1000 s association time and 100 sdissociation time. Data traces were corrected by subtraction of areference curve (antibody on biosensor, measurement with sample diluentonly), the Y-axis was aligned to the last 10 s of the baseline, andinterstep correction as well as Savitzky-Golay filtering was applied.Data traces with a response <0.05 nm were excluded from analysis.

Table 5 shows the association rate constant k_(a) (1/Ms), dissociationrate constant k_(d) (1/s) and equilibrium dissociation constant K_(D)(M) for recombinant CD3E determined by biolayer interferometry.IgG1-huCD3-FEAL showed a relatively high (K_(D): 15 nM) binding affinityto recombinant CD3E compared to IgG1-huCD3-H101G-FEAL (K_(D): 638 nM).

TABLE 5 Binding affinities of monospecific, bivalent CD3 antibodies torecombinant CD3ε as determined by label-free biolayer interferometryOn-rate Off-rate Antibody k_(a) (1/Ms) k_(d) (1/s) K_(D) (nM)IgG1-huCD3-FEAL 2.7E+05 4.0E−03  15 IgG1-huCD3-H101G-FEAL 3.0E+042.0E−02 683

Example 10—Generation of Bispecific Antibodies by 2-M E A-InducedFab-Arm Exchange

Bispecific antibodies were generated in vitro using the DuoBody®platform technology, i.e. 2-MEA-induced Fab-arm exchange as described inWO2011147986, WO2011131746 and WO2013060867 (Genmab) and Labrijn et al.(Labrijn et al., PNAS 2013, 110: 5145-50; Gramer et al., MAbs 2013, 5:962-973). To enable the production of bispecific antibodies by thismethod, IgG1 molecules carrying a single mutation in the CH3 domain weregenerated: in one parental IgG1 antibody the F405L mutation (i.e. theCD3 antibodies), in the other parental IgG1 antibody the K4098 mutation(i.e. the 5T4 or control, HIV-1 gp120-specific, antibodies). In additionto these mutations, the parental IgG1 antibodies included substitutionsthat result in a Fc domain that is unable to interact with IgG Fcreceptors (Fc gamma receptors) and complement: L234F, L235E, D265A(FEA).

To generate bispecific antibodies, the two parental antibodies weremixed in equal mass amounts in PBS buffer (Phosphate Buffered Saline;8.7 mM HPO₄ ²⁻, 1.8 mM H₂PO₄ ⁻, 163.9 mM Na⁺, 140.3 mM Cl⁻, pH 7.4).2-mercaptoethylamine-HCl (2-MEA) was added to a final concentration of75 mM and the reaction mixture was incubated at 31° C. for 5 h. The2-MEA was removed by dialysis into PBS buffer using 10 kDamolecular-weight cutoff Slide-A-Lyzer carriages (Thermo FisherScientific) according to the manufacturer's protocol in order to allowre-oxidation of the inter-chain disulfide bonds and formation of intactbispecific antibodies.

The following antibodies were used in the examples:

CD3 Antibodies

IgG1-huCD3-FEAL (having the VH and VL sequences set forth in SEQ ID NO:57 and SEQ ID NO: 60).

IgG1-huCD3-H101G-FEAL (having the VH and VL sequences set forth in SEQID NO: 68 and SEQ ID NO: 60)

ST4 Antibodies

IgG1-5T4-207-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 40 and SEQ ID NO: 44)

IgG1-5T4-226-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 47 and SEQ ID NO: 51)

IgG1-5T4-059-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 5 and SEQ ID NO: 9)

IgG1-5T4-076-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 12 and SEQ ID NO: 16)

IgG1-5T4-085-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 19 and SEQ ID NO: 23)

IgG1-5T4-106-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 26 and SEQ ID NO: 30)

IgG1-5T4-127-FEAR (having the VH and VL sequences set forth in SEQ IDNO: 33 and SEQ ID NO: 37)

IgG1-5T4-H8-FEAR (based on 5T4 antibody H8 from Wyeth (WO 2007/106744and US2010/0173382); having the VH and VL sequences set forth in SEQ IDNO: 87 and SEQ ID NO: 88)

IgG1-5T4-A1-F405L (based on 5T4 antibody A1 from Wyeth (WO 2007/106744and U.S. Pat. No. 8,044,178); having the VH and VL sequences set forthin SEQ ID NO: 83 and SEQ ID NO: 84)

IgG1-5T4-A1-FEAR (based on 5T4 antibody A1 from Wyeth (WO 2007/106744and U.S. Pat. No. 8,044,178); having the VH and VL sequences set forthin SEQ ID NO: 83 and SEQ ID NO: 84)

IgG1-5T4-A3-F405L (based on 5T4 antibody A3 from Wyeth (WO 2007/106744and U.S. Pat. No. 8,759,495); having the VH and VL sequences set forthin SEQ ID NO: 85 and SEQ ID NO: 86)

IgG1-5T4-A3-FEAR (based on 5T4 antibody A3 from Wyeth (WO 2007/106744and U.S. Pat. No. 8,759,495); having the VH and VL sequences set forthin SEQ ID NO: 85 and SEQ ID NO: 86)

Bispecific Antibodies

bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-076-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-085-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-127-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR

bsIgG1-huCD3-H101G-FEALx5T4-H8-FEAR

bsIgG1-huCD3-H101G-FEALxb12-FEAR

bsIgG1-huCD3-FEALx5T4-207-FEAR

bsIgG1-huCD3-FEALx5T4-226-FEAR

bsIgG1-huCD3-FEALx5T4-059-FEAR

bsIgG1-huCD3-FEALx5T4-106-FEAR

bsIgG1-huCD3-FEALx5T4-H8-FEAR

bsIgG1-huCD3-FEALx5T4-A1-FEAR

bsIgG1-huCD3-FEALx5T4-A3-FEAR

bsIgG1-b12-FEALx5T4-207-FEAR

Fluorescein Isothiocyanate (FITC)-Labeled Bispecific Antibodies

bsIgG1-b12-FEALx5T4-059-FEAR-FITC

bsIgG1-b12-FEALx5T4-207-FEAR-FITC

bsIgG1-b12-FEALx5T4-226-FEAR-FITC

bsIgG1-5T4-A1-F405Lxb12-FEAR-FITC

bsIgG1-5T4-A3-F405Lxb12-FEAR-FITC

Duostatin-3 Conjugated Bispecific Antibodies

BsIgG1-5T4-H8-FEARxb12-vcDuo3

bsIgG1-5T4-076-FEARxb12-vcDuo3

bsIgG1-5T4-085-FEARxb12-vcDuo3

bsIgG1-5T4-127-FEARxb12-vcDuo3

BsIgG1-5T4-059-FEARxb12-vcDuo3

bsIgG1-5T4-106-FEARxb12-vcDuo3

bsIgG1-5T4-207-FEARxb12-vcDuo3

bsIgG1-5T4-226-FEARxb12-vcDuo3.

Non-Binding Control Antibodies

IgG-b12 is a HIV-1 gp120 specific antibody (Barbas, C F. J Mol Biol.1993 Apr. 5; 230(3):812-23) that is used in some of the examples asnegative, non-binding, control second arm for bispecific antibodies.

IgG1-b12-F405L is a variant hereof with the substitution F405L.

IgG1-b12-FEAL is a variant hereof with substitutions that result in a Fcdomain that is unable to interact with IgG Fc receptors (Fc gammareceptors) and complement, in addition to a mutation that allows thegeneration of bispecific antibodies through controlled Fab-arm exchange:L234F, L235E, D265A and F405L.

IgG1-b12-K409R is a variant hereof with the substitution K409R.

IgG1-b12-FEAR is a variant hereof with substitutions that result in a Fcdomain that is unable to interact with IgG Fc receptors (Fc gammareceptors) and complement, in addition to a mutation that allows thegeneration of bispecific antibodies through controlled Fab-arm exchange:L234F, L235E, D265A and K409R.

Example 11—Binding of CD3×5T4 Bispecific Antibodies to Cynomolgus Monkeyand Human 5T4 Expressed in HEK-293 Cells

Binding of bispecific, monovalent CD3×5T4 antibodies and monospecific,bivalent 5T4 antibodies to the plasma membrane of HEK-293 cellstransiently transfected with human 5T4 or with cynomolgus monkey (Macacafascicularis) 5T4 (generated as described in Example 1) was analyzed byflow cytometry.

Cells (3×10⁴ cells/well) were incubated in polystyrene 96-wellround-bottom plates (Greiner bio-one, cat. no. 650180) with serialdilutions of antibodies (ranging from 0.0137 to 10 μg/mL in 3-folddilution steps) in 100 μL PBS/0.1% BSA/0.02% azide (staining buffer) at4° C. for 30 min. Experiments were performed in technical duplicate.After washing twice in staining buffer, cells were incubated in 50 μLsecondary antibody at 4° C. for 30 min. As a secondary antibody,FITC-conjugated goat-anti-human IgG F(ab′)₂ (Southern Biotech, USA, cat.no. 2043-02) diluted 1:200 in staining buffer, was used in allexperiments. Cells were washed twice in staining buffer, re-suspended in30 μL staining buffer and analyzed on an iQue Screener (IntellicytCorporation, USA). Binding curves were analyzed using non-linearregression (sigmoidal dose-response with variable slope) using GraphPadPrism V7.02 software (GraphPad Software, San Diego, Calif., USA).

FIGS. 5A-5D (left panels) show that bispecific antibodiesbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (FIG. 5A),bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR (FIG. 5B),bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR (FIG. 5C) andbsIgG1-huCD3-H101G-FEALx5T4-H8-FEAR (FIG. 5D), that monovalently bind5T4, display dose-dependent binding to HEK-293 cells transfected withhuman 5T4, which was comparable to binding of monospecific, bivalent 5T4antibodies IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR, IgG1-5T4-059-FEAR andIgG1-5T4-H8-FEAR, respectively.

FIGS. 5A-5D (right panels) show that bispecific antibodiesbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (FIG. 5A),bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR (FIG. 5B), andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR (FIG. 5C), that monovalently bind5T4, display dose-dependent binding to HEK-293 cells transfected withcynomolgus monkey 5T4, which was comparable to binding of monospecific,bivalent 5T4 antibodies IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR andIgG1-5T4-059-FEAR, respectively. BsIgG1-huCD3-H101G-FEALx5T4-H8-FEAR andIgG1-5T4-H8-FEAR show poor binding to cynomolgus monkey 5T4, which is inline with Example 2 and experiments described in WO2007/106744. Asnegative control, IgG1-b12-K409R (3 μg/mL) was included in theseexperiments, which showed no binding to HEK-293 cells transfected witheither human or cynomolgus monkey 5T4.

-   -   In a second experiment, the staining was performed as described        above with minor adjustments. The cells were incubated with        serial dilutions of antibodies ranging from 0.000128 to 10        μg/mL, in 5-fold dilution steps. As a secondary antibody,        Phycoerythrin (PE)-conjugated goat-anti-human IgG F(ab′)2        (Jackson Immunoresearch, UK, cat. no. 109-116-098) diluted 1:200        in staining buffer, was used.

FIGS. 5E-5M show that antibodies bsIgG1-huCD3-H101G-FEALx5T4-207-FEARand IgG1-5T4-207-FEAR (FIG. 5E), bsIgG1-huCD3-H101G-FEALx5T4-226-FEARand IgG1-5T4-226-FEAR (FIG. 5F), bsIgG1-huCD3-H101G-FEALx5T4-059-FEARand IgG1-5T4-059-FEAR (FIG. 5G), bsIgG1-huCD3-H101G-FEALx5T4-106-FEARand IgG1-5T4-106-FEAR (FIG. 5H), bsIgG1-huCD3-H101G-FEALx5T4-076-FEARand IgG1-5T4-076-FEAR (FIG. 5I), bsIgG1-huCD3-H101G-FEALx5T4-085-FEARand IgG1-5T4-085-FEAR

-   -   (FIG. 5J), bsIgG1-huCD3-H101G-FEALx5T4-127-FEAR and        IgG1-5T4-127-FEAR (FIG. 5K), bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR        and IgG1-5T4-A1-FEAR (FIG. 5L),        bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR and IgG1-5T4-A3-FEAR (FIG.        5M) display dose-dependent binding to HEK-293 cells transfected        with human 5T4 (left panels) as well as HEK-293 cells with        cynomolgus monkey 5T4 (right panels). Again, the binding curves        of the bivalent, monospecific and bispecific, monovalent        antibodies display a similar trend between human and cynomolgus        5T4.

Example 12—Binding of CD3×5T4 Bispecific Antibodies to 5T4-PositiveHuman Tumor Cells

Binding of CD3×5T4 bispecific antibodies to the 5T4-expressing humantumor cell lines HeLa (cervix adenocarcinoma; ATCC, cat. no. CCL-2) andMDA-MB-231 (breast adenocarcinoma; ATCC, cat. no. HTB-26) cell line wasanalyzed by flow cytometry. Neither HeLa nor MDA-MB-231 cells expressCD3.

Cells (3×10⁴ cells/well) were incubated in polystyrene 96-wellround-bottom plates (Greiner bio-one, cat. no. 650180) with serialdilutions of antibodies (range 0.000152 to 3 μg/mL in 3-fold dilutionsteps) in 100 μL PBS/0.1% BSA/0.02% azide (staining buffer) at 4° C. for30 min. After washing twice in staining buffer, cells were incubated in50 μL secondary antibody at 4° C. for 30 min. As a secondary antibody,Fluorescein isothiocyanate (FITC)-conjugated goat-anti-human IgG F(ab′)₂(Southern Biotech, USA, cat. no. 2043-02) diluted 1:400 in stainingbuffer, was used for the first experiment. Next, cells were washed twicein staining buffer, re-suspended in 120 μL staining buffer and analyzedon a BD LSRFortessa FACS (BD Biosciences, USA). Binding curves wereanalyzed using non-linear regression (sigmoidal dose-response withvariable slope) using GraphPad Prism V7.02 software (GraphPad Software,San Diego, Calif., USA).

FIGS. 6A-6C (left panels) show that the CD3×5T4 bispecific antibodiesbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (FIG. 6A) andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR (FIG. 6B) display dose-dependentbinding to HeLa cells, with higher maximum binding than themonospecific, bivalent 5T4 antibodies IgG1-5T4-207-FEAR andIgG1-5T4-059-FEAR. For bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR (FIG. 6C)the maximum binding was similar to that of the monospecific, bivalent5T4 antibody IgG1-5T4-226-FEAR on HeLa cells.

FIGS. 6A-6C (right panels) show that the CD3×5T4 bispecific antibodiesbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (FIG. 6A),bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR (FIG. 6B) andbsIgG1-huCD3-H101G-FEALx5T4-226-FEAR (FIG. 6C) display dose-dependentbinding to MDA-MB-231 cells, with higher maximum binding than themonospecific, bivalent 5T4 antibodies IgG1-5T4-207-FEAR,IgG1-5T4-226-FEAR and IgG1-5T4-059-FEAR. The negative control antibodythat was included in these experiments, IgG1-b12-K409R (3 μg/mL), didnot show binding to HeLa and MDA-MB-231 cells.

In a second experiment, the staining was performed as described abovewith minor adjustments. The cells were incubated with serial dilutionsof antibodies, ranging from 0.000128 to 10 μg/mL, in 5-fold dilutionsteps. As a secondary antibody, Phycoerythrin (PE)-conjugatedgoat-anti-human IgG F(ab′)2 (Jackson Immunoresearch, UK, cat. no.109-116-098) diluted 1:200 in staining buffer, was used. FIGS. 6D-6K and6L-6S show that antibodies bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andIgG1-5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR andIgG1-5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andIgG1-5T4-059-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR andIgG1-5T4-106-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-085-FEAR andIgG1-5T4-085-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-127-FEAR andIgG1-5T4-127-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andIgG1-5T4-A1-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR andIgG1-5T4-A3-FEAR display dose-dependent binding to HeLa and MDA-MB-231tumor cells. In general, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR, IgG1-5T4-207-FEAR,IgG1-5T4-226-FEAR, IgG1-5T4-059-FEAR, IgG1-5T4-106-FEAR,IgG1-5T4-085-FEAR and IgG1-5T4-127-FEAR display binding at lowerantibody concentrations compared to bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR, IgG1-5T4-A1-FEAR andIgG1-5T4-A3-FEAR.

Example 13—Induction of T-Cell Activation, Cytokine Release andCytotoxicity In Vitro by CD3×5T4 Bispecific Antibodies Using Purified TCells as Effector Cells

CD3×5T4 bispecific antibodies were tested in an in vitro cytotoxicityassay using 5T4-positive tumor cell lines as target cells and purified Tcells as effector cells. T cells were derived from healthy human donorbuffy coats (Sanquin, Amsterdam, The Netherlands) and isolated using theRosetteSep human T cell enrichment cocktail (Stemcell Technologies,France, cat. no. 15061) according to the manufacturer's instructions. Todetermine the percentage of viable T cells after isolation (either totalT cells, CD4⁺ T cells or CD8⁺ T cells), a sample of the isolated T cells(2.5×10⁵ cells per condition) was stained for 30 min at 4° C. in aU-well 96-well plate (Cellstar, cat. no. 650180) using the followingantibodies: Pacific Blue-anti-CD3 (eBiosciences, clone OKT3),APC-Cy-anti-CD4 (eBiosciences, clone OKT4), AF700-anti-CD8 (Biolegend,clone RPA-T8) and viability marker FVS 510 (BD Biosciences) in 100 μLPBS/0.1% BSA/0.02% azide (staining buffer). Next, cells were washedtwice in staining buffer, re-suspended in 120 μL staining buffer andanalyzed on a BD LSRFortessa FACS (BD Biosciences, USA). The percentagesof CD3⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells for each of the donors used inthe cytotoxicity experiment are described in Table 6.

TABLE 6 Ratio CD3⁺, CD4⁺ and CD8⁺ T cells per donor % CD3+ % CD4+ within% CD8+ within Donor of viable cells CD3+ cells CD3+ cells A 91.2 84.211.8 B 77.8 78.3 18 C 97.6 78.1 19.6 D 92.6 77.3 15.5 E 99.2 78.4 20.3

MDA-MB-231 cells (16,000 cells/well) were seeded into flat bottom96-well plates (Greiner-bio-one, The Netherlands, cat. no. 655180) andleft to adhere for 4 hours at 37° C. T cells were added to tumor cellsat an E:T ratio=8:1. Serial dilutions of bispecific CD3×5T4 antibodiesor monospecific, bivalent 5T4 antibodies were added (final concentrationranging from 1000 to 0.0128 ng/mL; 5-fold dilutions) and plates wereincubated for 72 hours at 37° C. Next, 110 μL supernatants containing Tcells were transferred to U-bottom 96 Well culture plates (CellStar,cat. no. 650180). Plates were centrifuged (300×g) for 3 min at 4° C.,after which 75 μL of supernatant was transferred to a new plate forcytokine production measurement, and T cells were kept to assess T cellactivation markers (described below). Cytokine production induced by 0.2μg/mL CD3×5T4 bispecific antibodies was analyzed by a multiplex U-plexassay (MeSo Scale Discovery, USA, cat. no. K15049K) according tomanufacturer's instructions.

T cells were stained for T-cell markers CD3 (1:200; eBioscience, cloneOKT3, conjugated to eFluor450), CD4 (1:50; eBioscience, clone OKT4,conjugated to APC-eFluor780), CD8 (1:100; Biolegend, clone RPA-T8,conjugated to AF700) and T-cell activation markers CD69 (1:50; BDBiosciences, clone AB2439, conjugated to APC), CD25 (1:50; eBioscience,clone BC96, conjugated to PE-Cy7) and CD279/PD1 (1:50; Biolegend, cloneEH12.2H7, conjugated to BV605). Single stained samples with Ultracompbeads (54; Invitrogen, cat. no. 01-2222-42) were used for compensationadjustments of the flow cytometer. After 30 min of incubation at 4° C.,plates were washed three times with PBS/0.1% BSA/0.02% azide (stainingbuffer). Cells were resuspended in 120 μL staining buffer and analyzedusing a FACS Fortessa (BD Biosciences). Data were processed using FlowJo(BD Biosciences).

In parallel, the viability of the tumor cells was assessed usingResazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide). The adherent tumorcells were washed twice with PBS and incubated with 10% Resazurin (150μL, Life Technologies, The Netherlands, cat. no. DAL1100) in RPMI-1640(Lonza, Switzerland, cat. no. BE12-115F) medium containing 10% donorbovine serum with iron (Life Technologies, The Netherlands, cat. no.10371-029) and pen/strep (Lonza, cat. no. DE17-603E) for 4 h at 37° C.The absorbance was measured with an Envision multilabel plate reader(PerkinElmer, US). The absorbance of staurosporine-treated(Sigma-Aldrich, US, cat. no. S6942) tumor cell samples was set as 0%viability and the absorbance of untreated tumor cell samples was set as100% viability. The ‘percentage viable cells’ was calculated as follows:% viable cells=([absorbance sample−absorbance staurosporine-treatedtarget cells]/[absorbance untreated target cells−absorbancestaurosporine treated target cells])×100.

Dose-response curves, EC50 and IC50 values were analyzed usingnon-linear regression (sigmoidal dose-response with variable slope)using GraphPad Prism V7.02 software (GraphPad Software, San Diego,Calif., USA).

FIGS. 7A-7C show that bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR, bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR induced dose-dependent cytotoxicity(shown as decrease in % viable cells) in the 5T4-positive tumor cellline MDA-MB-231. Donor-to-donor variation was observed, but T cells ofboth donors induced maximum kill in the presence of 1 μg/mL CD3×5T4bispecific antibody. Monospecific, bivalent antibodiesIgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR and IgG1-5T4-059-FEAR did notinduce cytotoxicity. IC₅₀ values calculated from the graphs arepresented in FIG. 7D. The IC₅₀ value of bsIgG1-huCD3-FEALx5T4-207-FEARand bsIgG1-huCD3-FEALx5T4-059-FEAR were lower compared tobsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR, respectively. In contrast, theIC₅₀ value of bsIgG1-huCD3-FEALx5T4-226-FEAR was comparable tobsIgG1-huCD3-H101G-FEALx5T4-226-FEAR.

FIGS. 8A-8F show that bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR, bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR, bsIgG1-huCD3-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR, bsIgG1-huCD3-FEALx5T4-A3-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR induced T-cell mediated cytotoxicity(shown as decrease in tumor cell survival) in MDA-MB-231 cell line.Bivalent, monospecific antibodies IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR,IgG1-5T4-059-FEAR, IgG1-5T4-106-FEAR, IgG1-5T4-A1-FEAR andIgG1-5T4-A3-FEAR did not induce T-cell-mediated cytotoxicity. IC50values calculated from the graphs are presented in FIGS. 8G-8H. IC50values of the T-cell mediated cytotoxicity induced bybsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-FEALx5T4-059-FEAR and bsIgG1-huCD3-FEALx5T4-106-FEAR arelower than the IC50 values of bsIgG1-huCD3-FEALx5T4-A1-FEAR andbsIgG1-huCD3-FEALx5T4-A3-FEAR. Also, IC50 values of the T-cell mediatedcytotoxicity induced by bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-106-FEAR are lower than the IC50 values ofbsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR.

T-cell activation was determined by flow cytometry through staining foractivation markers PD1, CD25 and CD69 (FIGS. 9A-9C). Monospecific,bivalent antibodies IgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR andIgG1-5T4-059-FEAR did not induce upregulation of these T-cell activationmarkers, while bispecific antibodies bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR, bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR induced dose-dependent upregulationof PD1, CD25 and CD69. EC₅₀ values calculated from the graphs arerepresented in FIG. 9D. The EC₅₀ values for upregulation of PD1, CD25and CD69 by bsIgG1-huCD3-FEALx5T4-207-FEAR andbsIgG1-huCD3-FEALx5T4-059-FEAR were lower compared tobsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-059-FEAR, respectively. The EC₅₀ values forupregulation of CD25 and CD69 by bsIgG1-huCD3-FEALx5T4-226-FEAR werelower compared to bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR, while the EC₅₀value for PD1 upregulation was comparable betweenbsIgG1-huCD3-FEALx5T4-226-FEAR and bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR.

FIGS. 10A-10F show that bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR, bsIgG1-huCD3-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR, bsIgG1-huCD3-FEALx5T4-106-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-106-FEAR, bsIgG1-huCD3-FEALx5T4-A1-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR, bsIgG1-huCD3-FEALx5T4-A3-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR induced T-cell activation(exemplified in FIGS. 10A-10F by increase in % CD69⁺ T cells within theCD4⁺ and CD8⁺ T cell populations) when incubated with the MDA-MB-231cell line, while the bivalent, monospecific antibodiesIgG1-5T4-207-FEAR, IgG1-5T4-226-FEAR, IgG1-5T4-059-FEAR,IgG1-5T4-106-FEAR, IgG1-5T4-A1-FEAR and IgG1-5T4-A3-FEAR did not induceT-cell activation. EC50 values of three T-cell activation markers areshown in FIGS. 10G-10L. In general, the EC50 values of the T-cellactivation (increase in % CD69⁺, CD25⁺ and PD1⁺ cells within the CD4⁺and CD8⁺ T cell populations) induced by bsIgG1-huCD3-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-FEALx5T4-059-FEAR andbsIgG1-huCD3-FEALx5T4-106-FEAR are lower than the EC50 values ofbsIgG1-huCD3-FEALx5T4-A1-FEAR and bsIgG1-huCD3-FEALx5T4-A3-FEAR. Also,EC50 values of T-cell activation (increase in % of CD69⁺, CD25⁺ and PD1⁺T cells within the CD4⁺ and CD8⁺ T cell populations) induced bybsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-H101G-FEALx5T4-059-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-106-FEAR are lower than the EC50 values ofbsIgG1-huCD3-H101G-FEALx5T4-A1-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-A3-FEAR.

Production of the cytokines IL-10, IL-13 and TNF after exposure ofco-cultures of T cells and MDA-MB-231 cells to 0.2 μg/mL CD3×5T4bispecific antibodies was measured in culture supernatant, by multiplexU-plex assay. FIG. 11 shows the cytokine levels in the supernatant of Tcell-tumor cell co-cultures, after incubation with bispecificantibodies. Experiments were performed using T cells from two differenthealthy donors; FIG. 11A shows the results from co-cultures with T cellsderived from donor A, FIG. 11B shows the results from co-cultures with Tcells derived donor B. Bispecific antibodiesbsIgG1-huCD3-FEALx5T4-207-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR,bsIgG1-huCD3-FEALx5T4-226-FEAR, bsIgG1-huCD3-H101G-FEALx5T4-226-FEAR,bsIgG1-huCD3-FEALx5T4-059-FEAR and bsIgG1-huCD3-H101G-FEALx5T4-059-FEARall induced cytokine release, although the cytokine levels in Tcell-tumor cell co-cultures incubated with CD3×5T4 bispecific antibodiescontaining a IgG1-huCD3-H101G-FEAL-derived CD3-specific Fab-arm werelower than cytokine levels in co-cultures that had been incubated withbispecific antibodies containing a IgG1-huCD3-FEAL-derived CD3-specificFab-arm. The monospecific antibodies IgG1-5T4-207-FEAR,IgG1-5T4-226-FEAR and IgG1-5T4-059-FEAR did not induce any cytokinerelease.

Example 14—Induction of Cytotoxicity In Vitro by CD3×5T4 BispecificAntibodies Using PBMCs or Purified T Cells as Effector Cells at VaryingEffector to Target Ratios

To determine the efficiency of the T-cell-mediated kill of bispecificantibodies bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR in more detail, a cytotoxicityassay was performed as described in Example 13, with varying effector totarget cell (E:T) ratios. In addition, either peripheral bloodmononuclear cells (PBMCs) or isolated T cells were used as effectorcells. The ovarian cancer cell line SK-OV-3 (9,000 cells/well, ATCC,cat. no. HTB-77) was used as target cell line. PBMCs were isolated from40 mL of buffy coat of human blood (Sanquin) using a Ficoll gradient(Lonza; lymphocyte separation medium, cat. no. 17-829E) according to themanufacturer's instructions. T cells were isolated as described inExample 13. For PBMCs, the following E:T ratios were used: 1:2, 1:1,2:1, 4:1, 8:1 and 12:1. For isolated T cells, the following E:T ratioswere used: 1:2, 1:1, 2:1, 4:1 and 8:1. In each experiment, effectorcells from two separate donors were used. Table 7 provides an overviewof the percentage of CD3⁺, CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells in the PMBC orT-cell isolates for each of the donors (determined as described inExample 13).

TABLE 7 Ratio CD3⁺, CD4⁺ and CD8⁺ T cells per donor. % CD3 with viable %CD4⁺ within % CD8⁺ within Donor cell population CD3⁺ cells CD3⁺ cells C(PBMCs) 75 56.8 28.9 D (PBMCs) 60 63.2 32 E (T cells) 98.3 59.6 31.6 F(T cells) 97.2 70 26.4

As shown in FIG. 12, using effector cells from two different donors, E:Tratios from 4:1 to 12:1 resulted in efficient PBMC-mediated kill of theSK-OV-3 cells in the presence of bsIgG1-huCD3-FEALx5T4-207-FEAR orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR. At E:T ratios of 2:1 and lower,maximum kill of the SK-OV-3 cells was not achieved at the highestantibody concentration used (1000 ng/mL). A similar result was observedwhen isolated T cells were used as effector cells (FIG. 13). Usingeffector cells from two different donors, an E:T ratio of 4:1 and 8:1resulted in maximum T-cell-mediated kill of the SK-OV-3 cells in thepresence of bsIgG1-huCD3-FEALx5T4-207-FEAR orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR at the highest antibodyconcentration used (1000 ng/mL), whereas lower E:T ratios were notsufficient to induce maximum kill. The efficacy of the T-cell-mediatedkill induced by bsIgG1-huCD3-FEALx5T4-207-FEAR andbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR is thus dependent on a sufficientlyhigh E:T ratio.

Example 15—Anti-Tumor Activity of CD3×5T4 Bispecific Antibodies in aHumanized Immune System Mouse Xenograft Model

The in vivo anti-tumor efficacy of the CD3×5T4 bispecific antibodiesbsIgG1-huCD3-FEALx5T4-207-FEAR and bsIgG1-huCD3-H101G-FEALx5T4-207-FEARwas evaluated in humanized (tail vein injected CD34+ hematopoietic stemcells [HSC] at an age of 3-4 weeks) NOD.Cg-Prkdc^(scid)II2rg^(tm1Wjl)/SzJ (NSG-HIS) mice (obtained from The Jackson Laboratory)that were inoculated subcutaneously with human MDA-MB-231 tumor cells.Humanization of the immune system of NSG-HIS mice was confirmed 16 weekspost-engraftment by flow cytometry. Subsequently, NSG-HIS mice wererandomized in three groups (8 mice per group), based on HSC donor (#5239or #2328) and the percentage of human CD3+ T cells within the humanCD45+ population in peripheral blood (mean % hCD45+ and % hCD3+ cellsrespectively; 42% hCD45+ and 39% hCD3+ for the PBS group, 34% hCD45+ and25% hCD3+ for the bsIgG1-huCD3-FEALx5T4-207-FEAR group, and 36% hCD45⁺and 29% hCD3⁺ for the bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR). 5×10⁶MDA-MB-231 cells (in 100 μL PBS) were injected subcutaneously (SC) inthe flank of the mice; this was indicated as day 0 in the study. At day14, 18, 21 and 25, the mice were injected intravenously (IV) with either0.5 mg/kg antibody or PBS. Treatment groups are shown in Table 8. Tumorgrowth was evaluated twice per week (starting at day 14) using acaliper. Tumor volumes (mm³) were calculated from caliper measurementsas 0.52×(length)×(width)².

The results are shown in FIG. 14. FIG. 14A shows that bothbsIgG1-huCD3-FEALx5T4-207-FEAR (p<0.01) andbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (p<0.05) efficiently inhibitedtumor growth based on Mann-Whitney statistical analysis at day 43compared to the control group. Furthermore, statistical analysis of thetumor-free survival curves (Kaplan Meier plot, using a tumor size <500mm³ as a cut-off) using a Mantel Cox test demonstrated that thedifference in tumor-free survival was statistically different, showingincreased tumor-free survival in animals treated withbsIgG1-huCD3-FEALx5T4-207-FEAR (p<0.001) orbsIgG1-huCD3-H101G-FEALx5T4-207-FEAR (p<0.001) compared to the untreatedanimals (FIG. 14B).

TABLE 8 Treatment groups. Treatment Animals Antibody Dose days per groupPBS — 14, 18, 21, 25 8 bsIgG1-huCD3- 0.5 mg/kg 14, 18, 21, 25 8FEALx5T4-207-FEAR bsIgG1-huCD3-H101G- 0.5 mg/kg 14, 18, 21, 25 8FEALx5T4-207-FEAR

Example 16. Determination of the Contribution of 5T4 Amino Acid Residuesto Antibody Binding Using Alanine Scanning

Library Design

A human 5T4 (Uniprot ID Q13641) single residue alanine library wassynthesized (GeneArt, Thermo Fisher Scientific), in which all amino acidresidues in the extracellular domain of human 5T4 were individuallymutated to alanine, except for positions already containing an alanineor cysteine. To minimize the chance of structural disruption of theantigen, cysteines were not mutated. The library was cloned in the pMACexpression vector containing a CMV/TK-polyA expression cassette, anAmpicillin resistance gene and a pBR322 replication origin.

Library Production and Screening

The wild type 5T4 and alanine mutants were expressed individually inFreeStyle HEK293 cells according to the manufacturer's instructions(Thermo Fisher Scientific, cat. no. 12347-019). One day posttransfection, the cells were harvested. Approximately 80,000 cells wereincubated with 20 μL FITC-conjugated antibody (3 μg/mL; in FACS buffer(PBS [Lonza, cat. no. 6E17-517]+0.1% [w/v] BSA [Roche, cat. no.10735086001]+0.02% [w/v] sodium azide [NaN₃; EMELCA Bioscience, cat. no.41920044-3]); Table 9) at room temperature for 40 min. Subsequently,cells were washed twice by centrifugation using 150-180 μL FACS buffer.Cells were resuspended in 30 μL FACS buffer and stored at 4° C. untilanalysis by flow cytometry using an iQue screener (IntellicytCorporation).

The entire experiment was performed twice yielding duplicatemeasurements.

TABLE 9 Antibodies used in determination of the contribution of 5T4amino acid residues in antibody binding using alanine scanning.Antibodies monovalently binding to 5T4 were labeled with FITC (ThermoFisher Scientific, cat. no. 46425), prior to performing the experiment.IgG1-5T4-A1-F405L and IgG1-5T4-A3-F405L are surrogate A1 and A3antibodies, respectively, that were cloned into the human IgG1 backbonecontaining the F405L mutations. Hence, the surrogate A1 antibody has avariable region identical to that of the A1 antibody disclosed inWO2007106744. Likewise, the A3 surrogate antibody has a variable regionidentical to that of the A3 antibody disclosed in WO2007106744. In bothantibodies, the Fc domain carries the F405L substitution. Test orcontrol Antibody antibody bsIgGl-b12-FEALx5T4-059-FEAR-FITC Testantibody bsIgGl-b12-FEALx5T4-207-FEAR-FITC Test antibodybsIgGl-b12-FEALx5T4-226-FEAR-FITC Test antibodybsIgG1-5T4-A3-F405Lxb12-FEAR-FITC Test antibodybsIgG1-5T4-A1-F405Lxb12-FEAR-FITC Control antibody used fornormalizationData Analysis

For every sample, the average amount of antibody bound per cell wasdetermined as the geometric mean of the fluorescence intensity (gMFI)for the viable, single cell population. The gMFI is influenced by theaffinity of the antibody for the 5T4 mutant and the expression level ofthe 5T4 mutant per cell. Since specific alanine mutations can impact thesurface expression level of the mutant 5T4, and to correct forexpression differences for each 5T4 mutant in general, data for eachtest antibody were normalized against the binding intensity of anon-cross blocking 5T4-specific control antibody, using the followingequation:

${{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} = {{Log}_{10}\left( \frac{{gMFI}_{{Test}\mspace{11mu}{Ab}}}{{gMFI}_{{Control}\mspace{11mu}{Ab}}} \right)}$

In which ‘aa position’ refers to the position that was mutated into analanine; and the Z-score was calculated to express loss or gain ofbinding of the antibodies, according to the following calculation:

${Z - {{score}\left( {{fold}\mspace{14mu}{change}} \right)}} = \frac{{{Normalized}\mspace{14mu}{gMFI}_{{aa}\mspace{11mu}{position}}} - \mu}{\sigma}$Where μ and a are the mean and standard deviation of the Normalized gMFIcalculated from all mutants.

If the gMFI of the control antibody for a particular 5T4 mutant waslower than the mean gMFIControl Ab-2.5×SD of the mean gMFIControl Ab(from all mutants), data were excluded from analysis (it was assumedthat expression levels for those 5T4 mutants were not sufficient to drawconclusions). This was the case for amino acid W at position 296 (SEQ IDNO: 1).

Results

FIG. 15 shows the binding results of the tested antibodies to human 5T4variants with single alanine mutations in the ECD: positions 32 to 355(according to SEQ ID NO: 1). The results indicate that antibodybsIgG1-b12-FEALx5T4-059-FEAR-FITC showed loss of binding when aa R atposition 73, T at position 74, Y at position 92, R at position 94, N atposition 95 or F at position 138 of human 5T4 were mutated to analanine. This suggests that binding of antibody IgG1-5T4-059-04-FEAR isat least dependent on aa R73, T74, Y92, R94, N95, F138 of human 5T4 (SEQID NO: 1), antibody bsIgG1-b12-FEALx5T4-207-FEAR-FITC showed loss ofbinding when aa S at position 69, Rat position 73, Y at position 92, Rat position 94, F at position 111, F at position 138, D at position 148of human 5T4 were mutated to an alanine. This suggests that binding ofantibody IgG1-5T4-207-FEAR is at least dependent on aa S69, R73, Y92,R94, F111, F138 and D148 of human 5T4 (SEQ ID NO: 1), antibodybsIgG1-b12-FEALx5T4-226-FEAR-FITC showed loss of binding when aa R atposition 73, Y at position 92, R at position 94, F at position 111, F atposition 138, L at position 144 or D at position 148 of human 5T4 weremutated to an alanine. This suggests that binding of antibodyIgG1-5T4-226-FEAR is at least dependent on aa R73, Y92, R94, F111, F138,L144 and D148 of human 5T4 (SEQ ID NO: 1), antibodybsIgG1-5T4-A3-F405Lxb12-FEAR-FITC showed loss of binding when aa D atposition 60, Q at position 61, D at position 88, L at position 89, Y atposition 92, F at position 111, P at position 115, L at position 117, Fat position 138, D at position 148 or N at position 152 of human 5T4were mutated to an alanine. This suggests that binding of antibodyIgG1-5T4-A3-FEAR is at least dependent on aa D60, Q61, D88, L89, Y92,F111, P115, L117, F138, D148 and N152 of human 5T4 (SEQ ID NO: 1).

Some amino acids might be indirectly involved in binding. For example,mutating a hydrophobic residue to alanine might impact the local foldingand affect the positioning of directly interacting residues (Zhao etal., 2014 Structure 22, 612-620). Based on structural data (human 5T4crystal structure 4 cnm; RCSB protein databank) the following residuesare buried and therefore expected to indirectly contribute to bindingto:

-   -   antibody bsIgG1-b12-FEALx5T4-059-04-FEAR-FITC: F138,    -   antibody bsIgG1-b12-FEALx5T4-207-FEAR-FITC: F111, F138, D148,    -   antibody bsIgG1-b12-FEALx5T4-226-FEAR-FITC: F111, F138, L144,        D148,    -   antibody bsIgG1-5T4-A3-F405Lxb12-FEAR-FITC: L89, F111, L117,        F138, D148, N152.

Since only surface-exposed residues can directly interact with theantibody, the following residues are expected to directly interact with:

-   -   antibody bsIgG1-b12-FEALx5T4-059-FEAR-FITC: R73, T74, Y92, R94        and N95,    -   antibody bsIgG1-b12-FEALx5T4-207-FEAR-FITC: S69, R73, Y92 and        R94,    -   antibody bsIgG1-b12-FEALx5T4-226-FEAR-FITC: R73, Y92 and R94,    -   antibody bsIgG1-5T4-A3-F405Lxb12-FEAR-FITC: D60, Q61, D88, Y92        and P115.

Together, these results propose that antibodies IgG1-5T4-059,IgG1-5T4-207 and IgG1-5T4-226 all bind by direct interaction with aminoacid residues R73, Y92 and R94. The results also indicate thatantibodies IgG1-5T4-059, IgG1-5T4-207 and IgG1-5T4-226 each bind to aepitope which is different from but partially overlapping with theepitope bound by IgG1-5T4-A3. This is in line with the displacementbehavior described in Example 3 and 4.

Example 17: Induction of T-Cell Activation and Cytotoxicity by CD3×5T4Bispecific Antibodies in Cell Lines of Different Indications In Vitro

CD3×5T4 bispecific antibodies were tested in an in vitro cytotoxicityassay using tumor cell lines of pancreas and cervical cancer as targetcells and purified T cells as effector cells. For each indication(pancreas cancer and cervical cancer) two representative cell lines wereselected. The tumor cell lines used in the in vitro cytotoxicity assayare summarized in Table 10. T cells were derived from human donor buffycoats (Sanquin, Amsterdam, The Netherlands) and isolated using theRosetteSep human T cell enrichment cocktail (Stemcell Technologies,France, cat. no. 15061) according to manufacturer's instructions. Foreach cell line, at least three different donors were tested in the invitro cytotoxicity assay and T-cell activation analysis, as summarizedin Table 10.

TABLE 10 Tumor cell lines used for in vitro cytotoxicity assay Tumorcell ATCC T-cell line Indication clone no. cytotox (n) activation (n)BxPC-3 Pancreas CRL-1687 3 3 PANC-1 Pancreas CRL-1469 9 4 Ca SkiCervical CRL-1550 5 3 SiHa Cervical HTB-35 3 3

Tumor cells (16,000 cells/well) were seeded into flat-bottom 96-wellplates (Greiner Bio-One, The Netherlands, cat. no. 655180) and left toadhere at 37° C. for 4 h. T cells were added to tumor cells at an E:Tratio=4:1. Serial dilutions of bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR orcontrol antibodies (bsIgG1-huCD3-H101G-FEALxb12-FEAR,bsIgG1-b12-FEALx5T4-207-FEAR) were added (final concentration rangingfrom 5000 to 0.0128 ng/mL; 5-fold dilutions) and plates were incubatedat 37° C. for 72 h. Next, 110 μL supernatants containing T cells weretransferred to round-bottom 96-well culture plates (CellStar, cat. no.650180) and centrifuged (300×g) at 4° C. for 3 min. T cells were stainedfor T-cell markers by incubation with CD3-eFluor450 (1:200; eBioscience,clone OKT3), CD4-APC-eFluor780 (1:50; eBioscience, clone OKT4),CD8-AF700 (1:100; Biolegend, clone RPA-T8) and T-cell activation markersCD69-APC (1:50; BD Biosciences, clone AB2439), CD25-PE-Cy7 (1:50;eBioscience, clone BC96) and CD279/PD1-BV605 (1:50; Biolegend, cloneEH12.2H7) diluted in 50 μL PBS/0.1% BSA/0.02% azide (staining buffer).Single stained samples with Ultracomp beads (54; Invitrogen, cat. no.01-2222-42) were used for compensation adjustments of the flowcytometer. After 30 min of incubation at 4° C., plates were washed threetimes with staining buffer. Cells were resuspended in 120 μL stainingbuffer and analyzed using a FACS Fortessa (BD Biosciences). Data wereprocessed using FlowJo (version 10, BD Biosciences).

In parallel, the viability of the tumor cells was assessed usingResazurin (7-Hydroxy-3H-phenoxazin-3-one 10-oxide). The adherent tumorcells were washed twice with PBS and incubated with 10% Resazurin (150μL; Life Technologies, The Netherlands, cat. no. DAL1100) in RPMI-1640medium (Lonza, Switzerland, cat. no. BE12-115F) supplemented with 10%donor bovine serum with iron (Life Technologies, The Netherlands, cat.no. 10371-029) and pen/strep (Lonza, cat. no. DE17-603E) at 37° C. for 4h. The absorbance was measured with an Envision multilabel plate reader(PerkinElmer, US). The absorbance of staurosporine-treated(Sigma-Aldrich, US, cat. no. S6942) cells were set as 0% viability andthe absorbance of untreated cells were set as 100% viability. The‘percentage viable cells’ was calculated as follows:% viable cells=([absorbance sample−absorbance staurosporine-treatedtarget cells]/[absorbance untreated target cells−absorbancestaurosporine treated target cells])×100.

Cytotoxicity curves, T-cell activation curves, IC50 (cytotoxicity) andEC50 (T-cell activation) values were analyzed using non-linearregression (sigmoidal dose-response with variable slope) using GraphPadPrism V7.02 software (Graph Pad Software, San Diego, Calif., USA).

FIGS. 16A-16B show that bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR inducedcytotoxicity in a range of cell lines of different indications, whilethe control bispecific antibodies (bsIgG1-huCD3-H101G-FEALxb12-FEAR,bsIgG1-b12-FEALx5T4-207-FEAR) targeting only the tumor cells or the Tcells did not show any cytotoxicity. FIG. 16C shows the mean IC₅₀ valuesfor each of the cell lines tested with different donors (at least n=3).FIGS. 17A-17D show the T-cell activation induced bybsIgG1-huCD3-H101G-FEALx5T4-207-FEAR in a range of cell lines ofdifferent indications as measured by the upregulation of CD69 on CD4⁺and CD8⁺ T cells (% of CD69⁺ cells within the CD4⁺ or CD8⁺ population).The control bispecific antibodies (bsIgG1-huCD3-H101G-FEALxb12-FEAR,bsIgG1-b12-FEALx5T4-207-FEAR) targeting only the tumor cells or the Tcells, did not induce any T-cell activation. FIGS. 17E-17F show the meanEC₅₀ values for each of the cell lines tested with different donors (atleast n=3).

These data indicate that bsIgG1-huCD3-H101G-FEALx5T4-207-FEAR canspecifically induce T-cell mediated cytotoxicity and T-cell activationin pancreas and cervical cancer, while control bispecific antibodiesbsIgG1-huCD3-H101G-FEALxb12-FEAR and bsIgG1-b12-FEALx5T4-207-FEAR do notinduce T-cell activation and T-cell mediated cytotoxicity.

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The invention claimed is:
 1. An antibody which binds to human 5T4 andcomprises a heavy chain variable (VH) region and a light chain variable(VL) region, wherein the VH region comprises the CDR1, CDR2, and CDR3sequences set forth in SEQ ID NOs: 41, 42, and 43, respectively, and theVL region comprises the CDR1, CDR2, and CDR3 sequences set forth in SEQID NO: 45, the sequence DAS, and SEQ ID NO: 46, respectively.
 2. Theantibody according to claim 1, which comprises a VH region comprising asequence having at least 90% sequence identity to the sequence of SEQ IDNO: 40 and a VL region comprising a sequence having at least 90%sequence identity to the sequence of SEQ ID NO:
 44. 3. The antibody ofclaim 1, which comprises a VH region comprising the amino acid sequenceset forth in SEQ ID NO: 40 and a VL region comprising the amino acidsequence set forth in SEQ ID NO:
 44. 4. The antibody of claim 1, whichis a monoclonal antibody.
 5. The antibody of claim 1, which is a fulllength antibody.
 6. The antibody of claim 1, which comprises a humanIgG1 constant region.
 7. The antibody of claim 1, which comprises akappa light chain constant region or lambda light chain constant region.8. A bispecific antibody comprising a first heavy chain and a firstlight chain comprising a first antigen-binding region corresponding tothe antigen-binding region of the antibody of claim 1, and a secondheavy chain and a second light chain comprising a second antigen-bindingregion.
 9. A bispecific antibody comprising a first heavy chain and afirst light chain comprising a first antigen-binding regioncorresponding to the antigen-binding region of the antibody of claim 2,and a second heavy chain and a second light chain comprising a secondantigen-binding region.
 10. A bispecific antibody comprising a firstheavy chain and a first light chain comprising a first antigen-bindingregion corresponding to the antigen-binding region of the antibody ofclaim 3, and a second heavy chain and a second light chain comprising asecond antigen-binding region.
 11. The bispecific antibody of claim 8,wherein the second antigen-binding region binds to human CD3.
 12. Thebispecific antibody of claim 11, wherein the second antigen-bindingregion comprises a VH region comprising the CDR1, CDR2, and CDR3sequences set forth in SEQ ID NOs: 54, 55 and 67, respectively, and a VLregion comprising the CDR1, CDR2, and CDR3 sequences set forth in SEQ IDNO: 58, the sequence GTN, and SEQ ID NO: 59, respectively.
 13. Thebispecific antibody of claim 12, wherein the second antigen-bindingregion comprises a VH region comprising the amino acid sequence setforth in SEQ ID NO: 68 and a VL region comprising the amino acidsequence set forth in SEQ ID NO:
 60. 14. The bispecific antibody ofclaim 11, wherein the first antigen-binding region comprises a VH regioncomprising the amino acid sequence of SEQ ID NO: 40 and a VL regioncomprising the amino acid sequence of SEQ ID NO: 44, and the secondantigen-binding region comprises a VH region comprising the amino acidsequence of SEQ ID NO: 68 and a VL region comprising the amino acidsequence of SEQ ID NO:
 60. 15. The bispecific antibody of claim 14,which is a full length antibody.
 16. The bispecific antibody of claim15, which comprises a human IgG1 constant region.
 17. A bispecificantibody comprising a first heavy chain and a first light chaincomprising a first antigen-binding region which binds to human 5T4, anda second heavy chain and a second light chain comprising a secondantigen-binding region which binds to human CD3, wherein: (a) the firstantigen-binding region comprises a variable heavy chain (VH) regioncomprising the amino acid sequence set forth in SEQ ID NO: 40 and avariable light chain (VL) region comprising the amino acid sequence setforth in SEQ ID NO: 44, and (b) the second antigen-binding regioncomprises a VH region comprising the amino acid sequence set forth inSEQ ID NO: 68 and a VL region comprising the amino acid sequence setforth in SEQ ID NO: 60, wherein the bispecific antibody comprises ahuman IgG1 Fc region, and wherein the first heavy chain comprises aconstant region wherein the amino acid residues corresponding to L234,L235, D265 and F405 in a human IgG1 heavy chain according to EUnumbering are F, E, A and L, respectively, and the second heavy chaincomprises a constant region wherein the amino acid residuescorresponding to L234, L235, D265 and K409 in a human IgG1 heavy chainaccording to EU numbering are F, E, A and R, respectively, and whereinthe first light chain and second light chain comprise light chainconstant regions comprising the amino acid sequences set forth in SEQ IDNOs: 95 and 96, respectively.
 18. The bispecific antibody of claim 17,which comprises a Fab-arm of a first monoclonal antibody which binds tohuman 5T4, and a Fab-arm of a second monoclonal antibody which binds tohuman CD3, wherein the Fab-arm of the first monoclonal antibodycomprises the first heavy chain and the first light chain of thebispecific antibody, and wherein the Fab-arm of the second monoclonalantibody comprises the second heavy chain and the second light chain ofthe bispecific antibody.
 19. A bispecific antibody comprising a firstheavy chain and a first light chain comprising a first antigen-bindingregion which binds to human 5T4, and a second heavy chain and a secondlight chain comprising a second antigen-binding region which binds tohuman CD3, wherein: (a) the first antigen-binding region comprises avariable heavy chain (VH) region comprising the amino acid sequence setforth in SEQ ID NO: 40 and a variable light chain (VL) region comprisingthe amino acid sequence set forth in SEQ ID NO: 44, and (b) the secondantigen-binding region comprises a VH region comprising the amino acidsequence set forth in SEQ ID NO: 68 and a VL region comprising the aminoacid sequence set forth in SEQ ID NO: 60, wherein the bispecificantibody comprises a human IgG1 Fc region, and wherein the first heavychain comprises a constant region wherein the amino acid residuescorresponding to L234, L235, D265 and K409 in a human IgG1 heavy chainaccording to EU numbering are F, E, A and R, respectively, and thesecond heavy chain comprises a constant region wherein the amino acidresidues corresponding to L234, L235, D265 and F405 in a human IgG1heavy chain according to EU numbering are F, E, A and L, respectively,and wherein the first light chain and second light chain comprise lightchain constant regions comprising the amino acid sequences set forth inSEQ ID NOs: 95 and 96, respectively.
 20. The bispecific antibody ofclaim 19, which comprises a Fab-arm of a first monoclonal antibody whichbinds to human 5T4, and a Fab-arm of a second monoclonal antibody whichbinds to human CD3, wherein the Fab-arm of the first monoclonal antibodycomprises the first heavy chain and the first light chain of thebispecific antibody, and wherein the Fab-arm of the second monoclonalantibody comprises the second heavy chain and the second light chain ofthe bispecific antibody.
 21. A composition comprising the antibody ofclaim 1 and a carrier.
 22. A kit comprising the antibody of claim 1 andinstructions for use.